The colony of Augusta Emerita, which became present-day Mérida in Estremadura, was founded in 25 B.C. at the end of the Spanish Campaign and was the capital of Lusitania. The well-preserved remains of the old city include, in particular, a large bridge over the Guadiana, an amphitheatre, a theatre, a vast circus and an exceptional water-supply system. It is an excellent example of a provincial Roman capital during the empire and in the years afterwards.

Źródło: World Heritage Convention
http://whc.unesco.org/en/list/664