Two entries with the name Perilous Bridge.
Perilous Bridge
Another name for the Sword Bridge leading to the land of Gorre.
Lancelot crossed it in his quest to rescue Guenevere.
Source
Vulgate Lancelot | 1215-1230
Perilous Bridge
Pont Perileus
A half-finished bridge on the way to the Castle Orguelleus.
Perceval had to cross i, and when he reached the end, it detached itself from one side of the chasm, turned 180 degrees, and allowed Perceval to keep riding to the other side. This was only to happen when the best of knights rode upon it.
Sources
Second Continuation of Chrétien’s Perceval | Attributed to Wauchier of Denain, c. 1200
The Elucidation | 13th century