Roman Roman Concrete Endures in Spain!

The Romans used 'opus caementicium' or conrete as we know it to build the core of their buildings like this amphitheater. They used lime pebbles and river sand as well as medium sized amphibolites (a kind of rock) as the aggregate.

The well preserved amphitheater and theater exists today in Merida, Spain - an ancient Roman town built for retired soldiers.

Roman bridge and modern hydroelectric dam in Alcantara (below)