Lago di Tenno

Halfway between the Brenta Dolomites and Lake Garda, a small basin of water changes colour with the seasons, from bright turquoise in early summer to deep emerald by autumn. Lake Tenno was born when a landslide dammed a mountain stream some eight centuries ago, and today it remains celebrated for the purity and shifting colour of its water.

Why it matters

The Garda Trentino tourist authority describes the lake, which locals call the "laghet", as roughly 750 metres long, 400 metres wide and up to 47 metres deep, set at 570 metres above sea level. Its fame rests on three things. First, the colour: the water shifts between turquoise and emerald as the seasons and light change, an effect produced by its mineral content and clarity. Second, its origin: geologists read it as a landslide lake, formed when a huge slope collapse dammed the Rio Secco, probably between the eleventh and twelfth centuries, which makes it young in geological terms. Third, its condition: with only three houses on the shore and no polluting inflow, the water is exceptionally clean, and the beaches have held Blue Flag certification, most recently renewed in 2026. The lake is also the hydrological secret of the whole district, because it has no surface outlet and feeds the Magnone stream that powers the Varone Waterfall.

What to notice

The northern arm is shallowest, where the water appears palest. A small island near the shore can become a peninsula when the water level falls; the reserve records fluctuations of 10 to 15 metres over a year. The gravel fan where the Rio Secco enters the lake is an ecologically rich area, crossed above by a suspension bridge. A local legend says the landslide occurred at midday and that survivors founded a village named for "lunch"; the story explains the neighbouring hamlet's name.

Context and history

The lake's creation story is unusually well defined for a natural site: the official portal dates the damming landslide to around the eleventh or twelfth century, which means the landscape medieval travellers knew already contained the lake in roughly its present form. Because the basin has no surface outflow, its water filters slowly underground and re-emerges in the Magnone stream, the torrent that carved the gorge of the Varone Waterfall, so the lake and the waterfall are one hydrological system. Human pressure remained minimal for centuries; the three dwellings on the shore are the only buildings. Protection has recently been formalised: the surrounding area is now the Lake Tenno Local Nature Reserve, and the municipality records the lake as governed by a specific management plan. Recognition extends beyond the shoreline: Tenno belongs to the UNESCO Biosphere Alpi Ledrensi e Judicaria, approved by UNESCO in 2015, a ten-municipality territory stretching from the Brenta Dolomites down to Lake Garda.