The Acropolis, protected as a UNESCO World Heritage Site, is a window into the world of ancient Greece, a new building, the New Acropolis Museum, has opened in 2007 to showcase the ruins of old Athens. While home to many classical and neo-classical buildings, Athens also has its share of modern, avant-garde architecture, such as the futuristic Olympic Sport Complex, designed by Santiago Calatrava. The Danish architect Theofil Hansen has given the city three fine examples of neo-classical Ionic architecture in his buildings for the University, the New Academy and the National Library in the late 19th century.