The Kandertal is the valley that most visitors to Interlaken see only from a train window, on the way to Kandersteg or through the Lötschberg tunnel toward Valais. Two stops along it reward getting off: the Blausee, a small privately owned lake so clear and so blue it looks retouched, and Frutigen, a modest valley town that turned an engineering side-effect of Switzerland’s biggest rail tunnel into a working tropical farm. Neither takes all day. Neither is free. Both are honest about what they are, which is rarer than it should be in this part of Switzerland.
What makes this pairing work
Blausee and Frutigen sit five minutes apart by car and are usually visited as a single outing, but they have almost nothing in common beyond geography. The Blausee is a nature experience with a paywall around it: a forest walk, a lake, boats, trout on the menu. Frutigen’s Tropenhaus is the opposite, an industrial curiosity dressed up as a visitor attraction, built on the fact that a tunnel bored through a mountain produces a surprising amount of warm water. Doing both in one day gives you contrast rather than repetition, and neither site demands hiking boots.
The Blausee: a lake that really is that colour
The Blausee (literally “blue lake”) lies in a patch of forest above the valley floor near Kandersteg, in the municipality of Kandergrund. It is small, no more than a few hundred metres across, and you can walk all the way around it in fifteen to twenty minutes. The colour is not a filter or a postcard trick: fine particles of calcium carbonate, washed down from the surrounding limestone, stay suspended in the water and scatter light the way clay particles do in some glacial lakes, but the effect here is a saturated turquoise-blue rather than the milky grey-green you get on Lake Brienz. On a sunny day with the water still, it is genuinely striking; under flat cloud it goes duller and greyer, closer to ordinary.
The lake has been privately owned and run as a paying attraction for well over a century, and the family that manages it has built a small but complete operation around it: a fish farm supplying the on-site restaurant with trout raised in the lake itself, a boathouse renting out rowing boats with glass panels set into the hull so you can watch the trout beneath you, and a shop selling smoked fish, local cheese and the kind of souvenirs that are at least made regionally.
None of this is subtle marketing, and the entrance fee (charged per person to walk into the park, roughly CHF 10 for an adult, less for children, worth checking on arrival since it is reviewed periodically) buys access to private land, not a natural feature you could otherwise see for free. Some visitors resent paying to look at a lake; most who have been find the fee reasonable once they see the upkeep of the paths, jetties and gardens.
The restaurant, Hotel-Restaurant Blausee, serves trout in several forms — smoked, pan-fried, poached — sourced directly from the farm a few metres away, at prices typical for a sit-down Swiss restaurant (a main course runs roughly CHF 28–42). It is not cheap, but the supply chain is about as short as restaurant food gets in Switzerland. If you would rather picnic, benches around the shore are free to use once you have paid the entrance fee, though bringing your own food into the restaurant terrace itself is not the done thing.
Rowing boats, glass-bottomed, seat two to four people and are rented in half-hour blocks, typically CHF 20–28 depending on the season and boat size. They only operate when the lake is ice-free and the boathouse is staffed, broadly late April to late October; outside that window the lake is still open to walk around, often looking sharper in cold, still winter light, but there is nothing to rent and the restaurant may run reduced hours.
a guided Blausee visit paired with a fondue meal bundles the entrance fee, a walk around the lake and a proper Swiss dinner into one booking, which suits anyone who would rather not work out the logistics themselves.
Getting to the Blausee
There is no train station at the lake itself. The routes in:
| From | Method | Approx. time | Notes |
|---|---|---|---|
| Interlaken Ost | Train to Spiez, change to Frutigen or Kandersteg, then PostBus | 50–65 min | Bus stop “Blausee” on the Kandersteg–Kandergrund route |
| Kandersteg station | PostBus | 5–8 min | Runs regularly through the day |
| Kandersteg station | On foot | 60–75 min | Signposted valley path, flat but unshaded |
| By car | Drive to the Blausee car park | — | Paid parking on site, fills up on summer weekends |
If you are travelling on a Swiss Travel Pass, the train and PostBus legs are covered; the lake’s own entrance fee is not, since it is a private attraction rather than a transport link.
Frutigen and the Tropenhaus: farming on tunnel water
Frutigen itself is an unremarkable, functional valley town, worth a stop for exactly one reason: the Tropenhaus. When BLS bored the 34.6-kilometre Lötschberg Base Tunnel between 1999 and 2007, the rock at depth turned out to be warmer and wetter than expected. Groundwater seeping into the tunnel near Frutigen emerges at a near-constant 18–20°C, roughly 100 litres per second, water that was originally simply discharged into the Kander river, warming it enough to concern local biologists. Rather than waste it, the operators piped it to a purpose-built greenhouse complex on the valley floor, and Tropenhaus Frutigen opened in 2009 running almost entirely on heat that would otherwise have been thrown away.
Inside, the greenhouse grows bananas, papaya, mango and other tropical species that have no business surviving at 630 metres of altitude in the Bernese Oberland, watered and warmed by tunnel outflow year-round. The more commercially significant part of the operation is the sturgeon farm: the same warm water sustains tanks of sturgeon, which take seven to ten years to mature and produce roe. The resulting caviar is sold under the brand Oona, and Frutigen is now one of a handful of places in Switzerland producing caviar domestically rather than importing it — a genuine novelty rather than a marketing invention, and priced accordingly (a small jar, around 30 grams, typically costs CHF 90–130, in line with farmed caviar elsewhere).
Visitors can tour the greenhouse and the fish hall, watch feeding where scheduled, and buy produce, fish and caviar in the shop. The on-site restaurant serves dishes built around the farm’s own sturgeon and the greenhouse’s tropical fruit, alongside more conventional Swiss plates. Entrance to the exhibition (excluding the restaurant) runs roughly CHF 12–16 for adults, with family and child rates; the whole visit, exhibition plus a browse of the shop, takes about an hour to ninety minutes.
an outdoor puzzle trail through Frutigen is a different way to spend an hour or two here if the greenhouse alone feels thin for a full visit, working the town’s streets and riverside into a scavenger-hunt format that works reasonably well with children.
Getting to Frutigen
| From | Method | Approx. time |
|---|---|---|
| Interlaken Ost | Direct or one-change train via Spiez (BLS line toward Kandersteg/Brig) | 30–38 min |
| Spiez | Direct train | 10–12 min |
| Kandersteg | Direct train | 10 min |
The Tropenhaus is roughly a 10-minute walk from Frutigen station, signposted from the platform; there is no need for a car or bus to reach it once you are in town.
Combining both in a single day
A realistic sequence from Interlaken:
| Time | Stop | Activity |
|---|---|---|
| Morning | Interlaken Ost → Frutigen | Train via Spiez, arrive mid-morning |
| Late morning | Tropenhaus Frutigen | Greenhouse, sturgeon hall, shop |
| Midday | Frutigen → Blausee | Bus or onward train + bus |
| Early afternoon | The Blausee | Walk the shore, boat hire if in season, lunch at the lakeside restaurant |
| Afternoon | Blausee → Kandersteg or back to Interlaken | Bus back to Kandersteg station, train home, or continue on to Kandersteg and the Oeschinensee if time allows |
Doing it in the other order works just as well; the deciding factor is usually the restaurant booking, since the Blausee’s terrace fills up at midday in summer and a table is worth reserving ahead if you want lunch there specifically.
What the day actually costs
| Item | Approx. cost (CHF, per adult) |
|---|---|
| Train + bus, return from Interlaken | 45–60 (less with a Swiss Travel Pass or Half Fare Card) |
| Blausee entrance | 10 |
| Boat hire (30 min, shared across 2–4 people) | 5–7 per person |
| Tropenhaus Frutigen entrance | 12–16 |
| Lunch (one sit-down meal) | 25–40 |
| Small caviar jar, if buying | 90–130 |
A day without the caviar souvenir lands around CHF 60–90 per person including transport and one meal, in line with most mid-range days out from Interlaken and cheaper than a mountain excursion involving a cable car.
If it’s raining
This is one of the better wet-weather pairings in the region, alongside the ideas in things to do in Interlaken when it rains. Tropenhaus Frutigen is entirely indoors and unaffected by weather. The Blausee walk is outdoors and exposed, but short enough to do in a raincoat, and the restaurant terrace has a covered section; a wet day simply means skipping the boats, which are less appealing anyway once the water surface is disturbed by rain.
Nearby, if you have more time
The Kandertal connects easily to several other stops covered on this site. Kandersteg and the Oeschinensee is fifteen minutes further up the line and pairs naturally with a Blausee morning; see the Oeschinensee hiking guide and the dedicated Kandersteg and Oeschinensee day trip for route options.
Southward over the Bunderchrinde or by road via Adelboden, Adelboden, Lenk and the Simmental and Gstaad form a chain of villages that make a longer loop possible if you have a car or several days; see the Gstaad and Glacier 3000 day trip for that combination.
a private van tour taking in Kandersteg and the Oeschinensee covers this stretch of the valley for anyone arriving from further afield, such as Montreux, rather than starting from Interlaken.
For food themes that connect to both stops, see fondue and raclette in Interlaken and cheese dairies of the Bernese Oberland, which cover the more traditional dairy side of local food that the Blausee’s trout and Frutigen’s caviar sit alongside rather than replace.
For the wider transport picture, including passes that cover this route, see the Swiss Travel Pass guide; for driving instead of the train, driving and parking in the Jungfrau region covers the practicalities, and this outing also appears among the wider day trips from Interlaken.
Frutigen and the Blausee: frequently asked questions
How do I get from Interlaken to the Blausee?
Take the train from Interlaken Ost to Spiez, change onto the BLS line toward Kandersteg, get off at Frutigen or Kandersteg, then take the connecting PostBus signposted “Blausee.” The full journey takes 50–65 minutes depending on connections. There is no direct train to the lake.
How much does it cost to enter the Blausee?
The park charges an entrance fee of roughly CHF 10 for adults, with reduced rates for children, on top of any transport cost. Boat hire and food are extra. The fee has been reviewed periodically over the years, so treat it as approximate rather than fixed.
Can you swim in the Blausee?
No. Swimming is not permitted, partly because the lake is a working trout farm and partly because it is managed as a scenic and dining destination rather than a swimming spot. For lake swimming nearby, see swimming in Lake Thun and Lake Brienz.
What is Tropenhaus Frutigen and why is it heated by a railway tunnel?
It is a commercial greenhouse and sturgeon farm built to use warm groundwater that flows out of the Lötschberg Base Tunnel near Frutigen, water that emerges at around 18–20°C as a by-product of the tunnel’s construction. Rather than discharge it into the river untreated, the operators redirected it to heat greenhouses growing tropical fruit and to raise sturgeon for caviar.
Can you actually buy the caviar made at Frutigen?
Yes. It is sold under the brand Oona in the on-site shop and in some Swiss retailers, priced like other farmed caviar — roughly CHF 90–130 for a small jar of around 30 grams. It is a genuine, if small-scale, domestic Swiss caviar operation rather than a rebranded import.
Is the Blausee worth it if it’s raining?
The lake and its short walk are outdoors and exposed, so rain takes the shine off the visit, though the walk itself is short enough to manage in waterproofs. Tropenhaus Frutigen is entirely indoors and makes a better rainy-day anchor for the trip; pair it with the Blausee only if the forecast allows.
How much time should I set aside for both?
Budget 45–90 minutes at the Blausee depending on whether you rent a boat or eat there, and 60–90 minutes at Tropenhaus Frutigen. With travel time between Interlaken and both sites, this comfortably fills a half-day and, with a proper lunch, most of a full day.
Do I need a car, or is this doable by public transport?
A car makes the logistics simpler, particularly getting to the Blausee car park directly, but both sites are reachable by train and PostBus without one, and a Swiss Travel Pass or Half Fare Card covers the transport legs. Public transport is the more common approach for visitors based in Interlaken.
