Today the most impressive former Roman city is Conimbriga, just to the south of Coimbra in the Centro region. The city was founded in the 9th century B.C. The Romans arrived in the 2nd century A.D. and the city flourished until it fell to barbarians in 468 A.D. Today Conimbriga is the best-excavated Roman site in Portugal. The site includes the foundations of numerous houses and public buildings, along with elaborate courtyards, fountains, hot and cold baths and mosaics. The public baths include a complex network of stone heating ducts beneath the floors.  

The most fascinating part of the site is the city walls that still stand. At one time, the peaceful Roman settlement had outgrown its walls and prospered beyond them. Then, when Germanic tribes began to attack in the 5th century, the people of city retreated and attempted to rebuild the crumbling walls with anything they could find--statues, bones, and pottery. The people lost that battle and the city was destroyed, however. Those who survived fled to nearby Aeminium, which is called Coimbra today--named for the bishop of the now ruined city of Conimbriga.

http://www.conimbriga.pt/index_en.html

HD Duecitânia Design Hotel opens in Penela (Centro) with Roman Theme