Built in the park belonging to Hainaut’s counts, on the site of the former château, the building nicknamed “el Catiau” towers over the city. From the garden, the view of Mons is simply stunning. From the top of the hill, you can imagine the history of this city, the trials that it has had to live through over the centuries, and its influence through time, until it became the capital of Hainaut. Next to the belfry, the Sainte-Calixte Chapel remains the city’s oldest religious monument. This Roman style chapel was built in 1051 and now houses a museum where you can learn about the history of the old château and the restoration undergone by the belfry.
https://www.visitmons.co.uk/see-do/top-sights/10-top-reasons-to-fall-in-love-with-mons/unesco/the-belfry