Arch of Caligula

View looking north at the Arch of Caligula (Roman Emperor, r. A.D. 37–41).  The Arch supported a statue of the (rather) unusual Emperor Caligula.  The Temple of Augustus is located at this intersection, and the street leading north toward snow–covered Mount Vesuvius is "via della Mercurio."

Note the "slits" on the side of the Arch.  They may have supported statues or "trophies" that exalted the divinity of the mad and cruel Caligula.