Royal Coliseum of Charles III Monument · San Lorenzo de El Escorial, Cuenca del Guadarrama, Madrid Opened in 1771 to a design by the French architect Jaime Marquet and later remodelled by Juan de Villanueva, it is the oldest surviving covered theatre in Spain and the only court theatre still in use. Marquet built the three court theatres of the Royal Sites of Aranjuez, El Pardo and San Lorenzo de El Escorial between 1770 and 1778, following a model inspired by classical Italian theatre; work on the San Lorenzo theatre began in 1771 and was finished the following year, before Villanueva remodelled it between 1784 and 1789. It retains the original 18th-century fly system above the stage. Declared a Bien de Interés Cultural (Spain's highest level of heritage protection) in 1995, it was restored in 1975, saving it from demolition, and reopened in 1979. Photo: Dorieo (CC BY-SA 4.0) What to see and do in San Lorenzo de El Escorial