In 1519, when the first Spaniards marched into the city of Tenochtitlán, it was the heart of the Aztec Empire. Founded on a lake island in 1325, the city was the nerve center of political and economic control of an extensive area of the Americas. More than 200,000 people lived in an urban area measuring almost 15 square kilometers (5 square miles), which included approximately 80 civil and religious buildings. The most important of these was the Templo Mayor, or Main Temple, on the crest of which were found two shrines; one dedicated to the god of war Huitzilopochtli and the other to the rain god Tláloc. Today, one can still see the temple's pyramidal base, enlarged seven times in 200 years. To one side of the site is the Casa de Caballeros Aguila, or the House of the Men-Eagle, which once housed an ancient order of elite warriors. A museum, called Museo del Templo Mayor, dedicated to the temple was set up in 1987 to preserve and showcase the findings from archaeological sites of the shrine and around the main square. The four-story building inside the complex was designed by architect Pedro Ramírez Vázque and comprises of artifacts such as the stone disk of Coyolxauhqui, urns, musical instruments and knives.

The Metropolitan Cathedral or Catedral Metropolitana is one of the most important historical buildings in Mexico City. Construction was started at the beginning of the 18th Century and continued throughout the next 300 years. This is why different influences can be detected in the architectural style, dominated by Spanish Renaissance and French Neoclassicism, along with a Baroque touch to the sandstone roof. The cathedral's five aisles are adorned with ornate altars and elaborate engravings, and its floors are made of marble. Visitors to Mexico City must not miss this transcendental symbol of Mexican art, history and heritage.

Originally the Dominican priests had a school on this site, but in 1711 the church of Porta Coelli supplanted the school. A Black Christ, which was venerated here until being moved to the Cathedral, lies here. Legend has it that a knight who had been poisoned by a treacherous friend, entered the church to kiss the then white holy image. The figure of Christ supposedly absorbed the poison, saving the knight's life, but at the cost of its complexion. Another tale, backed this time by historical evidence, is linked to Friar Servando Teresa de Mier, who carried out his ecclesiastical duties at Porta Cali: his fate was to be imprisoned by the Inquisition for questioning the appearance of the Virgin of Guadeloupe.

One of the greatest losses of Mexico City's cultural inheritance is related to the convent of San Francisco. The expansion of the city center, along with the Latin-American Tower construction project, had the dire effect of leaving only a small part of the cloister and church intact. The House of Beasts, or rather, Emperor Montezuma's zoological collection, originally occupied this land. After the Spanish conquest, Hernán Cortes gave it to the Franciscans (the first order to establish itself in what was then called New Spain), who built a 32,490 square meter convent, the biggest in America. Part of the installation included the school of Artes y Oficios (Skills and Trades) of San Jose de los Naturales, which aimed to educate indigenous children.

One of the most revered shrines of the Virgin Mary, the Basilica of Our Lady of Guadalupe is visited by thousands each year. The site of the Basilica at Tepeyac Hill is believed to be where the Virgin Mary appeared before Juan Diego, a Christian convert in 1531. All doubts about the veracity of his claims were laid to rest when the image of the Virgin Mary miraculously appeared on his cloak. The original shrine at the site was replaced by what is now known as the Antigua Basilica, completed in 1709. The stunning edifice of this historic church is richly inlaid with vivid sculptures, topped by a yellow dome and flanked by four towers. As word of the miraculous cloak spread, the basilica came to be a much-revered place of pilgrimage demanding the construction of a larger church in 1976 to accommodate the growing flock. The Nueva Basilica was built next door upon a spectacular, circular plan of mammoth proportions, topped by a tent-like roof, the altar a showcase for the miraculous cloak that has been carefully preserved to this day. Nearby, the modest chapel marks the site where Juan Diego first sighted the apparition of the Virgin Mary alongside a garden with babbling waterfalls and sculptural depiction of the event. The Antigua Basilica now houses a museum with a fine collection of colonial artwork.