If you want a good clear shot of the Pantheon without the crowds of tourists, you have to go before the tour groups mob the piazza in front of the Pantheon.

The Pantheon was begun Marcus Agrippa during the reign of Augustus as a temple to all the gods of ancient Rome.
(Pan= all, Theos - Gods),
The original Pantheon burned in ca. 80 AD, and was rebuilt and finished by the Emperor Hadrian in 126 A.D
Hadrian thoughtfully credited Agrippa with the structure, as can be seen on the inscription below the pediment.

"M. AGRIPPA.L.F.COSTERTIUM.FECIT”
“Marcus Agrippa son of Lucius, having been consul three times made it”.

The pediment originally contained relief sculpture of the Battle of the Titans, and the underside of the porch roof was covered in bronze,
which was stripped during the 17th c. to provide bronze for the Baldechino in St. Peters.

In 608, the Pantheon was converted to a church by Pope Boniface VIII, and is still used for worship services,
though most tourists see it as a museum.
It houses the graves of the artist Raphael, as well as the tombs of Kings Victor Emmanual I and Umberto I.