Valencia was founded as a Roman colony in 138 BC. The city is situated on the banks of the Turia, on the east coast of the Iberian Peninsula, fronting the Gulf of Valencia on the Mediterranean Sea. Its historic centre is one of the largest in Spain, with approximately 169 hectares; this heritage of ancient monuments, views and cultural attractions makes Valencia one of the country's most popular tourist destinations. Major monuments include Valencia Cathedral, the Torres de Serrans, the Torres de Quart, the Llotja de la Seda (declared a World Heritage Site by UNESCO in 1996), and the Ciutat de les Arts i les Ciències (City of Arts and Sciences), an entertainment-based cultural and architectural complex designed by Santiago Calatrava and Félix Candela. The Museu de Belles Arts de València houses a large collection of paintings from the 14th to the 18th centuries, including works by Velázquez, El Greco, and Goya, as well as an important series of engravings by Piranesi. The Institut Valencià d'Art Modern (Valencian Institute of Modern Art) houses both permanent collections and temporary exhibitions of contemporary art and photography.