"An imposing example of Spanish Renaissance style, Royal Monastery of San Lorenzo de El Escorial, an unmissable landmark, was once the royal residence of the Spanish king. This massive complex is now a UNESCO World Heritage Site with an art gallery, manicured gardens galore, basilica, library, and architectural museum; in other words, there's something for everyone. Show up early or prepare for long lines—this is one of the most popular sites in town." - Ramsey Qubein