Thun Castle

Thun Castle rises on a hill directly above the old town of Thun, where the Aare river leaves Lake Thun and begins its run north through the Bernese lowlands toward Bern. The castle's square keep with its four corner turrets has been the defining element of the Thun skyline since approximately 1190, when Duke Berthold V of Zähringen — the same duke who founded the city of Bern — built it as part of the Zähringen dynasty's systematic fortification and urbanisation of what is now the Swiss Mittelland and the approaches to the Alpine passes.

The Zähringen are one of the most consequential medieval dynasties in Swiss history, though they are not always recognised as such. Between the 11th and 13th centuries, they founded or refounded a series of strategically positioned towns — Bern, Fribourg, Burgdorf, Murten, Thun itself — that became the nuclei of Swiss urban life and eventually the core members of what would become the Swiss Confederation. Thun Castle was their fortified control point for Lake Thun and the Aare valley; Bern was founded within the same decade. When the Zähringen male line died out in 1218, their territories passed to the Counts of Kyburg and subsequently to the Habsburg family before Thun was purchased by the city of Bern in 1384, beginning a period of Bernese administration that shaped the castle's later development.

The castle's museum occupies the keep's four floors and covers Thun's history from prehistory through the 19th century. The centrepiece is the Knights' Hall on the second floor — one of the largest surviving medieval secular interiors in canton Bern, a vaulted room that served as the main ceremonial space of the medieval castle. The column arrangement and vault forms preserved here give a clear sense of how an important 12th-century fortified residence was designed: not as a purely military structure but as a functioning noble household with formal reception spaces appropriate to the Zähringen duke's social position.

The castle's terraces, reached by the same steep staircase that connects it to the old town below, give views south over Lake Thun and on clear days the entire arc of the Bernese Alps — Eiger, Mönch, Jungfrau visible as a distinct profile on the southern horizon. The old town of Thun below, with its distinctive two-storey arcaded main street elevated above the Aare, is one of the better-preserved small medieval towns in the Swiss Mittelland.

The GYG Lake Thun 3 Castles Tour (t1067418) covers Thun Castle alongside Oberhofen Castle and Spiez Castle in a 3.5-hour small-group programme from Interlaken, with all entry tickets included, English storytelling at each site, and hotel pickup. The three castles are collectively the most varied and complementary castle circuit in the Bernese Oberland.