Rota Porphyretica

In the Saint Peter’s Basilica in the Vatican there is a Red Porphyry disc towards the entrance of the Basilica on the center line of the church. It is named Rota Porphyretica (‘The Porphyry Wheel’).  The disc is one of the few remains of the Old Basilica, it dates back nearly 1700 years. It was originally located near the main altar of the old Saint Peter’s Basilica. Charlemagne knelt down on this very stone on Christmas night, year 800 AD. It was there that Pope Leo III crowned him Emperor of the Holy Roman Empire. Another 21 Emperors were crowned here.

Porphyry is a very hard rock which consists of purple groundmass containing small crystals of feldspar. The strength of this rock represents the strength of the Roman Empire, and the color represents royalty.

The majority of tourists who visit Saint Peter’s Basilica today have no idea what they are walking over, nor do they pay any attention to it. But centuries ago only the Papacy and Emperors were allowed to step foot on this stone.

http://www.anylatitude.com/2013/04/18/the-porphyry-disc-in-st-peter-where-charlemagne-was-crowned-in-the-year-800-is-still-there/

http://jloughnan.tripod.com/coronation.htm

http://www.thefreedictionary.com/porphyry