BREISACH, a town of Germany, in the Land of Baden, standing on a basalt rock 2 5of t. above the Rhine, 1 om. W. of Freiburg. Pop. 3,368. Breisach (Brisiacum), formerly an imperial city and until the 18th century one of the chief fortresses of the empire, is of great antiquity. A stronghold of the Sequani, it was captured in the time of Julius Caesar by Ariovistus and became known as the Mons Brisiacus. Fortified by the emperor Valentinian in 369 to defend the Rhine against the Germans, it remained throughout the middle ages one of the chief bulwarks of Germany and was called the "cushion and key (Kissen and Schliissel) of the German empire." It gave its name to the district Breisgau. In 939 it was taken by the emperor Otto I., and remained the exclusive possession of the emperors for two centuries. In 1254 and 1262 the bishops of Basle ob tained full control over it, but in 75 it was made an imperial city by King Rudolph I., and the Habsburgs possessed it from the 14th century. In the Thirty Years' War Breisach successfully resisted the Swedes, but it was forced to capitulate to the Protes tants after a memorable siege in 1638. The French held it from 1648, and it was several times besieged by them after its restora tion to Austria in 1697. By the peace of Pressburg (1805) it was finally incorporated with Baden, and the fortifications were razed. Two mediaeval gates, however, remain. It has a fine minster, partly Romanesque, partly Gothic, dating from the loth to the 15th centuries; one western tower is 13th century Gothic, the other Romanesque. The interior is remarkable for the wood carving of the high altar, and for tombs and pictures. There is little industry, but a considerable trade is done in wines and other agricultural produce. On the opposite bank of the Rhine, here crossed by a railway bridge, lies the little town of Neubreisach, built as a fortress by Louis XIV.