The Polvorín de Miraflores is an 18th-century structure in San Juan, Puerto Rico, specifically in the Isla Grande (Big Island) sector of Santurce, that served as an ammunition storage place for the Spanish military.

Among O'Reilly's recommendations was the construction of five ammunition storage (or polvorín) to support the other artillery structures on the island.

From that time until the 1930s, the Polvorín de Miraflores was used as a quarantine station under the administration of the United States Public Health Service.

Eventually, the building was taken by the Puerto Rico Department of Transportation and Public Works and the property was used for the storage of vehicles.

Recently, the structure was handed to the Convention Center District which prompted the removal of the abandoned vehicles from the property.