Mont-de-Marsan is a commune of France, prefecture (capital) of the Landes department.
The Donjon Lacataye is a the keep of a 14th century castle, constructed by order of Gaston Phebus in the commune of Mont-de-Marsan in the Landes department of France. Today, it houses a museum.

La Cataye consists of two joined Romanesque houses, which one sees perfectly while entering the current museum whose central internal wall includes Romanesque windows, a sign that one of the two houses was built before the second. These houses belonged to the Viscount’s family and were more or less abandoned starting from the 15th century, when the Viscounts moved away from their town of origin. During the 16th century, their upper parts were modified and they were equipped with crenelations. The material used is coquillere, a local sedimentary rock.

The name Cataye comes from the Spanish verb castar, to supervise. It is entirely possible that these houses replaced a preceding mound structure with tower because the site is also called: pujorin, i.e. pouy jorin ( pouy : height and jorin , deformation of lorenh : towards the east).

In 1860, Antoine Lacaze, mayor and owner of the keep, gave it to the town to house troops. It later became the departmental barracks until 1875, when the soldiers moved to the Bosquet barracks in the town. The keep preserved the name Caserne Lacaze (Lacaze Barracks) for nearly a century, in spite of a succession of civil uses: boarding school for young girls, gymnastics centre, municipal workshop.