Castillo San Cristóbal (San Juan)

Castillo San Cristóbal (English: Saint Christopher Castle) is a fortress in the Old San Juan historic quarter of San Juan, the capital municipality of Puerto Rico, known for being the largest fortification built by the Spanish in the New World. Dating back to defense expansions following attacks by the English in 1598 and Dutch in 1625, it was first constructed in 1634 as the Caballero de San Miguel (Saint Michael Cavalier) and the Garita del Diablo ("devil’s sentry box").

Source: Wikipedia — Castillo San Cristóbal (San Juan) (CC BY-SA 4.0)