The Triumphal Quadriga is the group of bronze four horses at St. Mark's Basilica. They were originally outside on the façade, but they have been replaced with replicas and moved inside for protection.
It is unclear when they were made, but it seems that they were brought to Constantinople and placed on the starting gates at the Hippodrome. It is possible that they originally had a chariot with a driver as part of the sculpture. However everything before its relocation to Venice is uncertain. It is clear that the Venetians brought the horses and later placed them on San Marco's façade after the Crusaders sacked Constantinople in 1204. While most of the bronze sculptures in Constantinople were melted down by the Crusaders, this piece is fortunately one of the few to survive. When Napoleon captured Venice, he brought them to Paris and placed it on the Arc de Triomphe du Carrousel, which is now topped with another quadriga. The Triumphal Quadriga have influenced many other quadriga as well.
Starting Gates of the Hippodrome
Quadriag replicas on the façade of San Marco
Arc de Triomphe du Carrousel
The Arc's Quadriga (1815)