Even with these proofs of early habitation, the history of Heerlen properly starts with the arrival of the Romans. They founded a military settlement, named "Coriovallum" on the crossroad of two main roads: Boulogne sur Mer - Cologne and Xanten - Aachen - Trier. In Heerlen and its surroundings a lot of evidence of Roman life has been excavated, especially Roman villas (country estates). The most notable archeological excavation from Roman times is the Thermae complex in the centre of Heerlen, a Roman bathhouse, discovered in 1940. In the Netherlands only a few of these have been found. It is a clear indication that Coriovallum/Heerlen was of some importance. A museum has been built over the Thermae and opened in 1977. The Thermenmuseum also houses other Roman finds from the area.