Sant’Angelo is the eleventh historic district or rione of Rome, often written as rione XI – Sant’Angelo. Its coat of arms is an angel on a red background, holding a palm branch in its left hand. In another version, the angel holds a sword in its right hand and a scale in its left. Sant’Angelo, the smallest of Rome’s rioni, lies along the Tiber river east of Tiber Island. Rioni bordering this district, clockwise from north to south, include Regola, Sant’Eustachio, Pigna, Campitelli, and Ripa. Sant’Angelo’s western border is the river. The rione’s terrain is low and flat and, until recent times, particularly susceptible to flooding from the river. The historical significance of Sant’Angelo is mainly the result of the presence here of the Roman Ghetto.