Festung Hohentwiel

Burchard II fortified the rock in 914 during his revolt against King Conrad I, and Conrad besieged it without success the year after — the siege that gives the mountain its first mention, as castellum tuiel, in the St Gallen chronicle of Ekkehard IV. Burchard prevailed, and around 920 Conrad's successor Henry I invested him with the duchy of Swabia.

Under his son Burchard III it became the Swabian ducal residence in mid-century, and work began in 970 on a monastery there dedicated to St George. He died in 973, and his widow Hadwig held the mountain for a further twenty-one years until her death in 994. Royal charters name her dux at a time when two other legitimate dukes were living, and she had Ekkehard II brought up from the abbey of St Gallen to teach her Latin.

Around 1005 the monastery moved to Stein am Rhein and the Twiel lost weight. By 1079 it plainly belonged to the Zähringen: Adelheid, wife of the anti-king Rudolf of Rheinfelden, died there that year. Ulrich von Eppenstein, abbot of St Gallen, took the mountain from Berthold II in 1086; after the abbot's death in 1121 the lords of Singen, in Zähringen service, took possession and styled themselves lords of Twiel.

On 16 February 1300 Ulrich von Klingen sold the Twiel to Albrecht von Klingenberg for 940 marks of silver, and it stayed with the Klingenbergs seven generations. A feud between Eberhard von Klingenberg and Johann von Werdenberg brought the Werdenbergers and the knights of the Sankt Jörgenschild to the mountain on 11 October 1464, though no serious fighting there is recorded; Archduke Sigismund of Austria mediated a peace at Biberach on 28 January 1465.

In 1511 Duke Ulrich of Württemberg obtained the right to occupy Hans Heinrich von Klingenberg's share of the Twiel, and when he fled the Swabian League in 1519 that right gave him refuge on it. In 1521 he secured the use of the mountain as the base for winning Württemberg back: by early 1525 five hundred Swiss mercenaries lay on the Hohentwiel and Ulrich had six to eight thousand men in the surrounding country, but the campaign broke off before Stuttgart when the French king's capture at Pavia caused the Swiss to be recalled.

Ulrich recovered his duchy nine years later, did not hand the castle back as agreed, and on 24 May 1538 bought it outright for 12,000 gulden. Having lost every castle he had when he was driven out, he meant to raise seven state fortresses, the Twiel among them, paid for with support from Francis I of France. Duke Christoph enlarged it in 1550.

After the defeat at Nördlingen on 6 September 1634 Württemberg lay open, Duke Eberhard III fled to Strasbourg, and every state fortress but the Hohentwiel fell to the imperial armies. Konrad Widerholt, made commandant that year, was largely thrown on his own resources; his correspondence with the exiled duke turns almost entirely on money and food, and he put the “useless” — women and children — off the mountain. Kidnapping was one means of raising money: the Sulz official Kullig, carried off from Jestetten in February 1635, brought 3,700 gulden, and horses seized in a failed attempt on the Bishop of Constance ransomed thirty-nine men taken in a fight for the Hohenkrähen.

The first siege ran from August 1635 to February 1636, while plague spread through the Hegau and killed 150 in the fortress, and ended in a bargain: an end to the raiding for the garrison's supply. When Eberhard III offered in 1637 to give the Hohentwiel to the emperor in return for his own restoration, Widerholt refused. Gottfried Huyn von Geleen besieged the place from July to October 1639, probably taking the outer court for a time; Spanish troops came in September 1640; and in the winter of 1641/42 imperial forces under Ernst Georg von Sparr and Gilles de Haes pushed close enough to bombard it, then lost heavily to the weather and broke off as relief under Johann Ludwig von Erlach approached. Franz von Mercy's blockade of 1644, the fifth, never assaulted the works and also failed.

The fortress was afterwards used as a state penitentiary, and in 1801, during the War of the Second Coalition, it was slighted. The ruins drew visitors almost at once. The Hohentwiel became part of Singen, the town 260 metres below, in 1969; at nine hectares it is the largest castle ruin in Germany open to tourists, and since 1990 more than 80,000 people have visited each year, a figure peaking at 126,520 in 2002. The Hohentwiel-Festival is held in the fortress area each year.