Mexico, perhaps surprisingly, has the Templo Mayo Aztec ruin in the middle of Mexico City
New Mexico has the Aztec Ruins National Park, with extensive remains – although the structures were built by the Pueblo people rather than Aztecs
Belize’s has numerous Mayan sites – Caracol is the best known, but there are also ruins at Altan Ha, which can easily be reached from Belize city.
El Salvador’s Tazumal Ruins are smaller than other ancient sites, but well preserved
Illinois has one of the oldest Native American remains at Monk’s Mound – although it’s a grass-covered hillock rather than built remains, and looks vaguely reminiscent of the remains of crude prehistoric forts in Europe
Mexico has some jaw-dropping Mayan sites, most notably on the Yucatan Peninsula. The famous Chichen Itza ruins are here. El Castillo appears in all the promotional photos, but there are numerous other sights of interest around the complex, including the Temple of Jaguars, Temple of Warrios and the baths. Although Chichen Itza can be visited as a day trip, there are plenty of cultural events held in the evening – you may want to stay for a few days to make the most of this amazing place. However, Chichen Itza isn't the only Mayan site on the Peninsula – you can also check out Tulum, Coda, Calakmul and many other temples in various states of restoration.
Peru's most famous Incan site is Machu Picchu. Trekking holidays to this fabled city are extremely popular, although you can also get there by train and bus. See the Sun Gate, the Temple of the Sun, and the Temple of the Condor. You're likely to be based in Cuzco – the city itself has plenty of historical places of interest. The Nazca Lines are another fascinating ancient sight, and no-one knows who etched these enormous geometric shapes into the desert, or why – some theories involve alien spaceships. While this sounds a bit wacky, it's true that the lines were only really 'discovered' after aircraft began to be used in the area. A flight in a light aircraft is the best way to see them – although there is an observation platform you can view them from too.
Colorado's Mesa Verde has some incredible and fascinating cliff-dwellings, built nearly one and a half millennia ago by a mysterious people called the Ancestral Puebloans. The best preserved is at Spruce Tree House, but there are numerous excavation areas and other buildings throughout the Mesa Verde National Park. There are also temples, and rock writings. The only way to get into some of the higher cliffs and more remote houses is on a ranger-guided tour – unsurprisingly, these feature some intensive but short bursts of climbing.
Honduras has some spectacular Mayan ruins at Copan. They have elaborate carvings and sculptures, and Mayan enthusiasts will easily be able to spend a couple of days examining the sights and art of the ruins. There's a reconstructed temple, a hieroglyphic stairway, and a museum full of diverting Mayan artefacts. The nearby town of Copan Ruinas has plenty of accommodation, and numerous more contemporary sights.
Guatemala's Tikal has some fantastic Mayan ruins that are popular with tourists, but not as mobbed as Chichen Itza and other better-known sites. The Temple of the Jaguar is the best-known of the builings here, and is a pyramid-type construction. There are two acropoli and a plaza to see too, as well as a clutch of museums. Seeing the site will take more than a day. There's also a jungle canopy tour available on-site, where you'll fly through the forest on zip slides.