Teotihuacan

Teotihuacan is in Mexico, a country in North America.

It is a city of ruins. There are big stone pyramids with steps. A long, wide road runs through the middle. Long ago, lots of people lived and worked here.

Teotihuacan lies in a valley about 50 kilometers northeast of Mexico City. Almost 2,000 years ago it was a great city, with plazas, palaces, houses and huge pyramids.

A long, straight avenue runs through the middle, with the giant Pyramid of the Sun beside it and the Pyramid of the Moon at its northern end. Around the year 500, Teotihuacan was one of the largest cities in the world. Its ideas, buildings and trade spread far across the region. Nobody knows for sure where its people came from or what language they spoke. Today it is a World Heritage Site.

Britannica calls Teotihuacan the largest and most important city of pre-Aztec central Mexico: at its apogee, about 500 CE, it covered some 20 square kilometers and is estimated to have held 125,000 to 200,000 people, making it one of the largest cities in the world at the time. UNESCO describes the city at its peak as stretching over 36 square kilometers and corresponding to at least 25,000 inhabitants; the estimates differ widely.

The city was the region's major economic and religious center. Its monuments line a north-south axis, the Avenue of the Dead, and UNESCO calls it a model of urbanization and large-scale planning that influenced later cultures. The origin and language of its people remain unknown. UNESCO listed it as a World Heritage Site in 1987.

The Pyramid of the Sun is the biggest building here. The Pyramid of the Moon stands at the end of the long road.

The road is called the Avenue of the Dead. Low buildings line both sides of it.

The Pyramid of the Sun rises about 66 meters, and its base is about 220 by 230 meters. It is one of the largest structures of its kind in the Western Hemisphere. The Pyramid of the Moon, the city's second-largest building, is 43 meters tall and stands at the northern end of the avenue.

The avenue is 40 meters wide and 2.4 kilometers long. Its name, the Avenue of the Dead, came much later; people once wrongly thought tombs lined it, but the low buildings along it were probably homes for important families. Farther south is the Ciudadela, or Citadel, a giant square courtyard.

The Pyramid of the Sun dominates the city from the east side of the Avenue of the Dead. Britannica gives it 66 m (216 ft) high and about 220 by 230 m at the base; UNESCO gives 75 m and 225 by 222 m. The Pyramid of the Moon, the second-largest structure, caps the avenue's north end at 43 m (140 ft), on a base of 130 by 156 m, with platforms and lesser pyramids around it and its main stairway facing the avenue.

The Avenue of the Dead, 40 m (130 ft) wide and 2.4 km (1.5 mi) long, runs slightly east of true north toward the nearby peak of Cerro Gordo; the low buildings along it, once thought to be tombs, were probably palace residences. The San Juan River was diverted to cross it. To the south, the Ciudadela is a square courtyard of about 15 hectares (38 acres), first excavated in 1917 to 1920.

Today, visitors walk along the great avenue.

Archaeologists are still digging. They keep finding houses, paintings and tunnels.

Today visitors walk the Avenue of the Dead between the pyramids. Digging began in 1884 and still goes on. In the 1960s and 1970s, a team made the first careful map of the whole city, and later teams explored tunnels and painted apartment buildings.

The ruins also face problems. Towns, shops, roads and a military base sit on parts of the old city, so protecting it is an ongoing job.

Excavation began in 1884. In the 1960s and 1970s the American archaeologist René Millon led the first systematic survey, the Teotihuacan Mapping Project; in 1980 to 1982 hundreds of workers excavated under the Mexican archaeologist Rubén Cabrera Castro, and 1990s work focused on the tunnels and the painted apartment compounds, some 2,000 of which have been identified.

Britannica lists long-standing threats to the wider zone of ruins: human settlement, including five towns, numerous shops, roads and highways, and a military base; many neighborhoods excavated in the late 20th century had earlier been farmed. UNESCO notes that the ceremonial center, despite its size, is only about 10 percent of the city's area, with residential districts such as La Ventilla, Tetitla and Tepantitla excavated beyond it.