The Roman Theater of Cartagena was built between the years 5 and 1 BC and at the time it had capacity for about 7.000 spectators. Currently, it houses the Museum of the Roman Theater, which was declared a Site of Cultural Interest in 1999. You have all the information in: «The 10 most important cities in Spain«.
You have all the information in: "The 10 most important cities in Spain".