La Catedral de San Cristóbal
Walking through Habana Vieja, just off Calle Obispo, you're likely to see the towers of La Catedral de la Virgen María de la Concepción Inmaculada de La Habana or La Catedral de San Cristóbal peering above the other buildings. Its Baroque-style facade was constructed using coral blocks cut from the floor of the Gulf of Mexico, giving it a bright white color from a distance. (And if you look up close, you can see marine fossils dotting it.) Inside, visitors can admire the vaulted ceiling and the statue of St. Christopher and seek out the area of the cathedral that is purported to have housed the relics of Christopher Columbus for almost the entirety of the 19th century (though this fact hasn't been proven). Afterward, if you haven't gotten your fill of the facade, grab a coffee or drink at one of the many cafés on the edge of the plaza to admire the view a bit more.