This structure on the Monceau hill, built between 1889 and 1890, is an integral part of the Belfont stronghold.

The entrance was via a drawbridge, followed by an imposing gate, with a removable floor separating the two and a metal door to secure the access.

It is one of the few modern structures built entirely of concrete, with a moat that can be filled with water during mobilisation by means of the sluice gates located on the Savoureuse river, thereby preventing enemy infantry assaults on the structure.