The Basilica of the National Shrine of the Immaculate Conception is numbered among the ten largest churches in the world. It measures a total of 459 feet long and covers an area of 77,500 square feet. The height of the nave, from the marble floor to the apex of the central dome is ten stories. The Knights' Tower, a gift of the Knights of Columbus and completed in 1959, rises 329 feet from ground level -- from its base to the top of the cross is as tall as a 32 story building