The town was strongly fortified by medieval walls, which have to some extent been demolished.
The town was built and fortified by Cosimo I.
In 1510, following their occupation of Oran and other towns on the coast of Africa, the Spaniards fortified the Penon.
Rhine, was strongly held by a series of fortified camps.
Restored to Prussia in 1816 it was again fortified, but in 1862 the fortifications were converted into a public park.