SPQR on the top of a sidewalk billboard in front of the Baths of Caracalla, opened in 216 AD. In ancient Rome it accommodated 8,000 people a day. Today it is one of the largest and best preserved of the ancient thermal complexes and during the summer it is used for opera productions.
SPQR are the first letters of the words in the Latin phrase Senatus Populusque Romanus, "The Senate and the People of Rome." It originally referred to the government of the ancient Roman Republic, and used as an official signature of the government, appearing on coins, stone and metal inscriptions, and on the standards of the Roman legions. SPQR is the motto of the city of Rome and appears in the city's coat of arms, as well as on many of the city's civic buildings, public fountains, manhole covers and billboards.