Burg Adolfseck, Castle ruin in Bad Schwalbach, Germany

Burg Adolfseck is a castle ruin perched on a rocky hilltop in Bad Schwalbach that preserves the remains of a medieval fortress with an oval-shaped core. The surviving walls show the layout of this former defensive structure, with its ground plan still clearly visible to visitors today.

The castle was first documented in 1356 and arose from the territorial expansion of the Nassau-Idstein family in the region. It served as a fortification for centuries before declining during the early modern period.

The castle's name comes from Count Adolf I of Nassau-Wiesbaden-Idstein, who was building it when Archbishop Gerlach of Mainz granted it to him as a fief on 18 February 1356. His brother Johann, later Archbishop of Mainz, had a chapel dedicated to Saint Valentine built inside the walls. In the 15th and 16th centuries the castle occasionally served as a widow's residence.

The ruin stands on a spur of the Aar at the southern edge of Adolfseck, a district of Bad Schwalbach, at 312 m above sea level. Only small remnants of walls and a well survive; the oval main castle can be read only in its ground plan. The whole complex is a protected monument, so stay on the paths.

The castle stood on a hill spur where a dammed loop of the Aar once formed a lake to the west, south and east. Its oval main ward measured about 55 by 40 metres, with a ring wall 1.3 to 1.5 metres thick and a six to eight metre wide zwinger added in the mid-14th century.