Bergfeste Dilsberg, Medieval fortress in Neckargemünd, Germany.

Bergfeste Dilsberg is a hilltop fortress on the 288.6-metre Dilsberg above the Neckar valley, split into an outer bailey and an inner bailey. The inner bailey is ringed by a curtain wall up to 16 metres high, entered past two flanking towers and an octagonal stair tower about 19 metres tall, built of reddish-brown stone blocks. Of the five-storey palas only the vaulted cellar, the Witch's Cellar, survives; the Commandant's House of around 1550 stands in the outer bailey.

A predecessor tower house was built between 1150 and 1200; the castle was first mentioned in 1208 in connection with Boppo V of Lauffen. After the Lauffen line died out, the Counts of Dürn held it and called themselves Counts of Dilsberg from 1252. Around 1300 it passed to the Electoral Palatinate, which rebuilt it extensively from the 1330s; Rupert I founded the town below and it received town rights in 1347.

The castle hosts the Dilsberger Kunsthandwerkermarkt craft market, the Dilsberger Burgkonzerte concerts, and open-air performances of 'Die Rose vom Dilsberg' in early summer. A youth hostel operates within the old town centre. The nearby Commandant's House, built around 1550, served as a school from 1894 to 1982 and became a cultural centre in 1997.

Access is available from March through October, Tuesday to Sunday, while visits from November to March need to be arranged in advance with the local tourist office. The path up to the site is steep, but once you arrive, you can walk around the entire grounds and explore all areas.

The 78-metre adit was driven from outside the hill to strike the well shaft after 65 metres, but the miners repeatedly lost direction, so it ended up 78 metres long. It was dug in the second phase to vent mining fumes, then filled in; locals spun it into a secret passage beneath the Neckar, a legend Mark Twain repeated in A Tramp Abroad.