Barcelona is home to two World Heritage Sites dedicated to architecture, but for most visitors only one of these will come to mind: the Works of Antoni Gaudí. This World Heritage Site only comprised three of Gaudí's works when first inscribed: Parque Güell, Palacio Güell, and Casa Mila. My friend and I rented go-karts to travel Barcelona when we visited in 2013, and we made a point to spend time exploring Parque Güell, which seems a bit like Lewis Carroll's Wonderland turned into stone and mosaics. As many have noted, the park offers a superb view of the city, although Barcelona is not lacking in overlooks. On our drive around Barcelona we passed by both Casa Mila and Casa Batlló (added to the World Heritage Site in a later extension); although we didn't go inside, the exteriors of both buildings are rather awe-inspiring. To me, though, the best of Gaudí's architecture is perhaps his most well-known work, the Sagrada Família, whose sand castle-like spires rise high above the city center. Only the Nativity Facade and the crypt are inscribed (also through the extension), but the entire church is a masterpiece of Gaudí's unique style of architecture, which seems in constant danger of melting or eroding away. I highly recommend climbing the towers to get a bird's eye view of Gaudí's designwork. Gaudí's plans for the church were scheduled to be finished around 2026, which makes me wonder whether construction will actually be completed at Sagrada Família before repairwork is completed at Notre-Dame de Paris.

Logistics: Barcelona has an excellent Metro system, which provides easy access to most of the inscribed works of Antoni Gaudí.