Hohentwiel

Hohentwiel is an extinct volcano in the Hegau region of Baden-Württemberg. It stands west of Singen and about ten kilometres from Lake Constance. The mountain rises 260 metres above the Aachtal Valley and is topped by the ruins of Hohentwiel Castle. The slopes are steep on the eastern side and flatter to the west. The softer rocks around the volcanic plug have been worn away by glaciers, leaving the harder phonolite exposed. The castle was built in 914 from stone quarried on the mountain by Burchard II, Duke of Swabia. It later passed to the von Singen-Twiel, von Klingen and von Klingenberg families before coming under Duke Ulrich of Württemberg in 1521. He turned it into one of the strongest fortresses in his duchy. The name ‘Hohentwiel’ first appears in 1521, though earlier forms such as ‘Tuiel’ and ‘Twiel’ appear in medieval records. Visitors reach the summit along paths through beech and oak woodland. The ruins include sections of curtain wall, a keep and the foundations of the former monastery of St Georg. From the top there are wide views across Lake Constance and the Hegau volcanoes. The contrast between the dark phonolite rock and the surrounding farmland is striking. On clear days the Alps can be seen to the south.