This section of the capital lies in the municipal borough of Cuauhtémoc, has just over nine square km and occupies 668 blocks. It contains 9,000 buildings, 1,550 of which have been declared of historical importance. Most of these historic buildings were constructed between the 16th and 20th centuries. It is divided into two zones for preservation purposes. Zone A encompasses the pre-Hispanic city and its expansion from the Viceroy period until Independence. Zone B covers the areas all other constructions to the end of the 19th century that are considered indispensable to the preservation of the area's architectural and cultural heritage.