The Roman Pantheon was a temple for all of the gods worshiped by the Romans. The word "pantheon" itself means "all gods" and is often used to refer to the group of gods the Romans worshiped. This word is also applied to other cultures' gods as well, like the Greeks' pantheon of gods.
The Pantheon was originally built by Agrippa, who was the heir of Caesar Augustus. The structure was built in 27 B.C, but burned in 80 A.D. Hadrian, the architect behind Hadrian's Wall in England, had the structure rebuilt complete with its dedication to Agrippa. The building is still in use today, but as a Catholic church where services are held daily.