The Citadel Namur is a fortress dates originally from the Roman era, but has been rebuilt several times. Its current form was designed by Menno van Coehoorn, and improved upon by Vauban after the siege of 1692. It has been classified as a Wallonia's Major Heritage site.
The original citadel dates to 937. It achieved its present extent between 1631 and 1675, when the city was under Dutch control. This section was called Terra Nova to distinguish it from the smaller fort built adjacent in 1542 and ensuing years. A variety of subsidiary positions were built in the 18th century. It was disestablished as a military post in 1891, superseded by a new ring of forts around Namur that were calculated to prevent the city from being attacked with artillery. This ring became the Fortified Position of Namur in the 1930s.
References:The Amphitheatre of the Three Gauls was part of the federal sanctuary of the three Gauls dedicated to the cult of Rome and Augustus celebrated by the 60 Gallic tribes when they gathered at Lugdunum (Lyon). The amphitheatre was built at the foot of the La Croix-Rousse hill at what was then the confluence of the Rhône and Saône.
Excavations have revealed a basement of three elliptical walls linked by cross-walls and a channel surrounding the oval central arena. The arena was slightly sloped, with the building"s south part supported by a now-vanished vault. The arena"s dimensions are 67,6m by 42m. This phase of the amphitheatre housed games which accompanied the imperial cult, with its low capacity (1,800 seats) being enough for delegations from the 60 Gallic tribes.
The amphitheatre was expanded at the start of the 2nd century. Two galleries were added around the old amphitheatre, raising its width from 25 metres to 105 metres and its capacity to about 20,000 seats. In so doing it made it a building open to the whole population of Lugdunum and its environs.