Rebuilt by Emperor Hadrian between 118 and 125 AD, the Pantheon in Rome is a exceptionally preserved ancient temple featuring the world's largest unreinforced concrete dome. Converted into a church in 609 AD, it stands as a premier example of Roman engineering, complete with an oculus for lighting and a portico of massive granite columns. For more details on the Pantheon's history, visit pantheonroma.com . History of the Pantheon in Rome and curiosities to discover