Old Havana is the heart of the city. It’s the place of the Historical Center and its system of fortifications. It has a rich architecture, one of the most conserved of America. The walking tour covers the four most important squares: Plaza de Armas, with baroque palaces surround the square such as the Palacio de los Capitanes Generales, now the Museo de la Ciudad; Plaza de San Francisco, with commercial buildings such as the old Stock Exchange and Customs House, and the Basilica de San Francisco as the main attraction, which dates back to 1580; Plaza Vieja, surrounded by pastel coloured town houses and almost completely restored; and Plaza de la Catedral, home to the exceptionally beautiful Catedral de San Cristóbal as well as important examples of early colonial architecture. All the squares are linked by historic streets, such as Calle Obispo, which are like open-air museums containing historic shops, museums and even a chocolate factory.