The architecture of Luxembourg appears to have its origins in the 1st or 2nd century BC when the Treveri, a prosperous Celtic tribe, developed an oppidum on Titelberg in the south-western corner of the country. The Romans, who occupied the area from 53 BC until the middle of the 5th century, are responsible for the remains of a number of villas across the country, especially in Echternach, Mamer and Goeblange. The Echternach site covers a huge area (118 by 62 metres), where there was a luxurious mansion from about 70 AD with 40 (later 60) rooms. It had balneae, a water heating system as well as additional buildings serving the surrounding farming community.