or Keil, a very important fortress of Germany, seated on the banks of the Rhine, built by the French after a design of Marshal Vauban, for the defence of Strasburg, from which it is a mile and a half distant. It was ceded to the empire in 1697, by the treaty of Ryawick. The French retook it in 1703, and it was restored to the empire by the treaty of Rastadt. During the time of the French revolution, this fortress changed masters several times; but after 1801, it was demolished in terms of the treaty of peace. E. Long. 7° 45'. N. Lat. 48° 40'.