Aquincum

Budapest has a rich history which is pretty much why such a large area of it is designated a UNESCO World Heritage Site.

The site stretches along the Danube up to Aquincum, which is the ruins of the ancient Roman settlement.

While the Roman town was rather large, the archaeological park is located at the remains of the civil town (the legionary fortress was further down the river).

Its quite a fascinating park with the excavated ruins of buildings and artifacts...even an amphitheater.
Check it out.