Pomparles Bridge crosses the River Brue just south of the town of Glastonbury. The derivation of the name "Pomparles Bridge" is from the French pont perilleux, "perilous bridge."
"A mile before [the river Brue] reaches Glastonbury, it comes to a bridge of four stone arches, which is known as Pontperlus, and it was here, according to legend, that King Arthur cast his sword into it"--John Leland's Itinerary
Before the draining of the region, the Pomparles Bridge area used to be underwater, and today the Pomparles Bridge only spans a small river. When the Somerset Levels were covered with water, the Glastonbury Tor became, in effect, an island. Many consider this to be the Isle of Avalon to which Arthur was taken to treat his mortal wounds from the battle at Camlann. It is not surprising therefore that there is an Excalibur legend concerning Pomparles Bridge.
Southern England Arthurian Sites