When I travel to places I tend to keep an eye out for fossils used in building materials. Recently while visiting St. Peter's Basilica in Vatican City near Rome, Italy I found some ammonite fossils in the floor slabs. This find was quite exciting since I could not find any documenting these elsewhere on the Internet. During my trip, I was the odd bird at sites around Italy studying/photographing the floor so much at famous/ornate sites while the other visitors were looking at the walls/ceiling/altars/statues.
The ammonites are embedded in several slabs in the floor. The slabs are near the Altar of St. Gregory the Great (590-604). They appear to be Rosso Ammonitico Lombardo (red polished limestone). As you can see by the close up images, the slabs are starting to have pieces removed from wear and tear.
Below is picture for the polished red rock strip to look for in the floor. There are two of them on either side of the alter that contained ammonite fossils.
If you get a chance to visit this remarkable church, try to visit this area and see these fossils for yourself.
UPDATE (2022): These ammonoids could date to the Upper Jurassic Period of the Rosso
Ammonitico Formation, Oxfordian Stage, Verona Province, Venetia Region
of Italy. This iron enriched (red) limestone is also known as Red Verona Marble or Rosso Verona Marble.
