"In Rome, the Pantheon, so great within and without, has overwhelmed me with admiration." --Goethe, 1786 The Pantheon is a magnificent ancient temple in Rome that was later converted into the church of Santa Maria ad Martyres. Dating from 125 AD, this is the most complete ancient building in Rome and one of the city's most spectacular sights.
This is a clear, easy-to-use site, that is also very informational. It includes a brief historical background on the building as well as a few interesting facts.
The Pantheon is the Roman monument with the greatest number of records: the best preserved, with the biggest brick dome in the history of architecture and is considered the forerunner of all modern places of worship. It is the most copied and imitated of all ancient works.