The Köppen Climate Classification subtype for this climate is "Hot-summer Mediterranean climate" "Csa" (Mediterranean Climate). The architecture of Valletta's streets and piazzas ranges from mid-16th century Baroque to Modernism. The city is the island's principal cultural center and has a unique collection of churches, palaces and museums and act as one of the city's main visitor attractions. When Benjamin Disraeli, future British Prime Minister, visited the city in 1830, he described it as "a city of palaces built by gentlemen for gentlemen," and remarked that "Valletta equals in its noble architecture, if it does not excel, any capital in Europe," and in other letters called it "comparable to Venice and Cádiz" and "full of palaces worthy of Palladio." Buildings of historic importance include St John's Co-Cathedral, formerly the Conventual Church of the Knights of Malta. It has the only signed work and largest painting by Michelangelo Merisi da Caravaggio. The Auberge de Castille et Leon, formerly the official seat of the Knights of Malta of the Langue of Castille, Léon and Portugal, is now the office of the Prime Minister of Malta. The Grandmaster's Palace, built between 1571 and 1574 and formerly the seat of the Grand Master of the Knights of Malta, used to house the Maltese Parliament, now situated in a purpose-built structure at the entrance to the city, and now houses the offices of the President of Malta. The National Museum of Fine Arts is a Rococo palace dating back to the late 1570s, which served as the official residence of the Commander-in-Chief of the Mediterranean Fleet during the British era from the 1820s onwards. The Manoel Theatre () was constructed in just ten months in 1731, by order of Grand Master António Manoel de Vilhena, and is one of the oldest working theatres in Europe. The Mediterranean Conference Centre was formerly the Sacra Infermeria. Built in 1574, it was one of Europe's most renowned hospitals during the Renaissance. The fortifications of the port, built by the Knights as a magnificent series of bastions, demi-bastions, cavaliers and curtains, approximately high, all contribute to the unique architectural quality of the city. Valletta contains a number of unofficial neighbourhoods, including:   The Valletta Campus of the University of Malta is situated in the Old University Building.