The old part of the city revolves around downtown and the four original neighborhoods from which the city expanded. The most notable building here is the Baroque Government Palace, dating from 1664 and constructed out of red volcanic stone; it is known for its one hundred arches. The prominent Baroque Cathedral, begun in 1575, is the oldest building in the city. The tall column in the center of the main square dates from colonial times; it held a statue of a Spain's viceroy, which was toppled when the country gained independence; the current sculpture on its summit commemorates Mexican independence.