Set astride the River Aare on the lake which bears its name, THUN (pronounced toon) is much overlooked by visitors pressing on to Interlaken. This is a shame, since with its picturesque castle and quaint medieval centre, it’s well worth a visit; views of the Eiger, Mönch and Jungfrau and, closer at hand, the giant pyramidal Niesen (2362m) and flat-topped Stockhorn (2190m) are a gentle prelude to the Alpine vistas further south.

The town has an odd secret, however. After World War II, the authorities decided that in the event of a future invasion, the whole of Switzerland south to Thun was to be abandoned, and the entire population was to assemble here for dispersal into mountain retreats. Switzerland’s largest hospital was hollowed out of the Niesen, but despite constant upkeep, has never been used; it remains pristine and fully equipped, and there are probably dozens of other major military and civil emergency installations hidden in the mountains nearby.

Across the river from the station, Thun’s low-lying Old Town – disastrously flooded in May 1999 – is renowned for the arcading both of the main street, split-level Obere Hauptgasse, and the tranquil, cobbled Rathausplatz at its northwestern end. Steps lead up from various points along the picturesque street to the fairy-tale turreted castle which looms above, built in 1190 and occupied by the Bernese in 1386. Its lofty halls now contains a historical museum (daily: June–Sept 9am–6pm; April, May & Oct 10am–5pm; Feb & March 1–4pm; Fr.5; SMP), with the usual period furniture and militaria.

At the lakeshore but on the station side of the river is the lush Schadau Park, home to perfectly tended flowerbeds, stunning views across the water to the mountains, and a lavish nineteenth-century folly planted majestically on the waterside. Beside it is an odd cylindrical building housing the Wocher Panorama (Tues–Sun: July & Aug 10am–6pm; May, June, Sept & Oct 10am–5pm; free), a giant painting – the oldest of its kind in the world – running all the way around the interior wall, which depicts the daily life of Thun circa 1810.