You are thinking of the Pantheon. It is a temple in Rome built in the first century, and it has a dome made of concrete. (The Parthenon on the other hand is a t

You are thinking of the Pantheon. It is a temple in Rome built in the first century, and it has a dome made of concrete. (The Parthenon on the other hand is a temple in the Acropolis in Athens, but not related to concrete)