It is built on the site of a pre-existing religious building dating back to the Longobard times
using blocks of travertine from the quarries next to the Tiber.
The Collegiate dates from the 11th and early 12th century, although
an inscription on the façade indicates the 12th century.
The porch is supported by four columns and two half-side columns on the capitals of which
there rests a lintel while above there are five low arches, which support the half-barrel roof.
Both the lintel and the arches are decorated by Cosmatescque mosaics, which few of them have survived.
Particularly interesting are some of the reliefs, characterized by a rare and enigmatic iconography.
On some areas still bearing the original mosaic decorations, the gold vitreous tesserae can still be found.
In the upper part of the façade there is a large typical Umbrian style rose window consisting of
two double rows of pillars flanked by mullioned windows and a smaller rose window above.
Interesting but not the only example, the glazed terracotta bowls coming from the Middle East.
In addition to the usual reliefs of the Evangelists and the Cosmatesque decorations
- some of these mosaics being totally replaced in a previous restoration -,
the rose window is also flanked by two griffons
that protrude significantly from the façade,
and an eagle crowns the
pinnacle of the