PBS
Pbs: The Pantheon
This site from PBS lists the vital statistics of this ancient wonder as well as an explanation of how it was built. Also has a comparison between modern domed buildings and the Pantheon.
Other
Rome Guide: Pantheon
This article discusses the architectural history of the Roman temple and provides photographs.
Other
Concrete and the Pantheon
Very detailed site explores the Pantheon with a scientific eye. It has many details about the process of building this wonder, the use of concrete, and why it has survived nearly 2000 years.
Other
The Temple of Aphaea at Aegina
A description of the structure Temple of Aphaea. Includes information about its loacation and use.