Most reviews have covered the Zocalo, the Palace of Fine Arts, and Templo Mayor. However, I noticed no mention of the Regina Cultural Corridor (Street) which is clearly included in the 2014 Map of the inscribed area. Indeed, I personally found this street one of the most interesting areas to explore in the historic district. The atmosphere was vibrant, the restaurants/cafes are quite good, and the corridor is littered with historical structures. Moreover, unlike the Zocalo, the street is not particularly catered toward tourists, and is frequented by locals.
Based on the 2014 map, it seems the Museo Diego Rivera, which includes his famous mural are not part of the inscribed zone. However, the Secretaria de Publica (Mexico City) is part of the inscribed zone, which also contains significant Diego Rivera Murals. Unfortunately, I walked to this building, but it was closed. Nearby is the Antiguo Colegio de San Ildefonso which is a tremendous structure filled with Orozco murals. There is a stunning Diego Rivera mural inside as well, but sadly it cannot be photographed. Exhibitions are showcased here, and during my visit there were unique "interactive" statues constructed by Michael Landy.
Lastly, I would mention the Gran Hotel which is tucked in a corner of the Zocalo. This hotel has one of the most brilliant glass ceilings I have ever seen. There is also a delicious, though pricey buffet at the top of the hotel, which overlooks the Zocalo. The beauty of the Historic Centre of Mexico City is its diverse array of attractions that go well beyond the Zocalo. From Aztec structures, Diego Rivera & Orozco murals, and countless Spanish colonial buildings - El Centro Historico has a bit of everything.