The Pantheon was built as a temple to the gods of Ancient Rome by Marcus Agrippa, a friend of Augustus', in 27 BC. However the original building burnt down in 80 AD. It was rebuilt by Hadrian and dedicated between 118 and 125AD.
It is the best preserved of all Roman buildings, and has been in continuous use throughout its history. It is also the oldest domed structure remaining in Rome. The height to the oculus and the diameter of the interior circle are the same: 43.3 metres.
Since the 7th century, the Pantheon has been used as a Roman Catholic Church, and is therefore also known as the Church of Santa Maria ad Martyres.
The term 'pantheon' can now be applied to any monument in which the illustrious dead are buried.