THE CABALLERO - All of the city of Old San Juan could be observed by troops on this highest level of San Cristobal, known in the 18th century as a "cavalier". From here rebel Spanish gunners took control of their cannons and aimed them at their neighbors in the city during an uprising in April 1855. The concrete observation post you see on the north side was built by the US Army during World War 11 for coastal defense. WHAT FLAG IS THAT? - Three flags customarily fly from the top of San Cristobal: the United States, Puerto Rico, and the "Cross of Burgundy", the flag of Spanish military units and warships from the 1500's to the 1780's   Fort San Cristóbal | El Morro | City Walls | Cañuelo