Among Genoa's notable buildings are the Cathedral of San Lorenzo (rebuilt in 1100 and frequently restored), the palace of the doges, the richly decorated churches of the Annunciation and of St. Ambrose (both 16th cent.), the medieval Church of San Donato, many Renaissance palaces, and the Carlo Felice opera house (19th cent.). The city is surrounded by old walls and forts, and the steep and narrow streets of the harbor section are very picturesque. The 16th-century Lanterna [lighthouse] is an emblem of Genoa. The Old Port was redesigned in 1992 by Renzo Piano; a modern aquarium and tropical greenhouse (the Bolla) are there. Genoa has several museums and a university (founded 1243).