Basilica of St. Patrick's Old Cathedral

Designed by Joseph-François Mangin — co-designer of New York City Hall — its cornerstone was laid June 8, 1809, and it was dedicated May 14, 1815; it served as the seat of New York's Catholic diocese until the Midtown St. Patrick's Cathedral opened in 1879, and Pope Benedict XVI named it a minor basilica in 2010. Its underground catacombs — 35 family crypts and 5 clerical vaults — are open for walking tours.