These ancient pyramids in Teotihuacan, 30 miles northeast of Mexico City, will take your breath away.
If the spectacle of a 2,200-year-old city doesn't do it, climbing 248 steep steps at 7,500 feet above sea level almost certainly will.
The climb is not mandatory, but it's the only way to get atop the Pyramid of the Sun, the best place to observe this two-mile stretch of streets, pyramids and temples of ornately carved stone.
Seeing these pyramids is the most popular out-of-town trip for travelers to Mexico City, a city which, despite its cultural and historic treasures, inspires an occasional day trip, if only for a breath of smog-free air.
At Teotihuacan, the air is usually clear, albeit thin. And sometimes, particularly on weekdays, the crowds are as thin as the air.
From on top of the Pyramid of the Sun, one looks down on the wide Avenue of the Dead, which stretches north between rows of small temples. Capped with tufts of grass, the structures blend into the backdrop of green hills and the nearby fields of agave, prickly-pear cactus and pepper tree.
At the north end of the avenue stands the bulky Pyramid of the Moon, somewhat shorter than the Pyramid of the Sun, but no less impressive.
The magic and appeal of Teotihuacan (Tay-oh-tee-wah-con) lies in the intriguing blend of what we do and do not know about it.
What we do know: Here, in the largest ruins of Ancient America, are the earthly remains of a highly ordered and well-organized civilization formed about 200 years before the birth of Christ.
At its peak, between 300 and 600 A.D., Teotihuacan had a population of about 250,000 and was one of the grandest cities in the world. We see a development that shows a sophisticated sense of art, architecture, astronomy, agriculture and irrigation.
The layout of buildings and streets, along north-south and east-west lines, reflects a sense of urban planning that would be the envy of a modern-day metropolis. With Teotihaucan's development, Mexico's Central Plateau emerged as the country's dominant region.
But equally fundamental are some things we don't know: Just who were these people, why did they build this city and why, about 750 A.D., did they abandon it?
For all their advancements and organization, the original residents of Teotihuacan left behind no evidence of a written language, not one word of explanation.
The very word "Teotihuacan," meaning "City of the Gods," comes not from the area's original residents, but from the Aztecs, who came here later, after the city was in ruins.
The Aztecs, it is said, were so overwhelmed by the majesty of the place that they were convinced this was a city dedicated to -- if not occupied by -- the gods.
What the Teotihuacan people have told us about themselves is conveyed in the detailed murals and carvings they left behind. Hardly a wall was left unadorned.
Chief among the gods here is Quetzalcoatl (ket-zal-coh-ah-tull), depicted as a feathered serpent, the god whose powers included authority over agriculture.
On the temple of Quetzalcoatl, the serpent is shown in a pattern along with Tlaloc, the big-eyed rain god -- a pattern said to encourage a happy relationship between the rains and the crops.
Many of these murals show aspects of the civilization's culture and beliefs. Absent is any depiction of war, conflict or human sacrifice, leading to the theory that for centuries, life in Teotihuacan was relatively tranquil.
The residents' knowledge of astronomy shows in orientation of the Pyramid of the Sun, situated so that sun sets directly in front of it on the summer solstice.
These days, strollers down the Avenue of the Dead will find it alive with commerce.
Walking the mile from Pyramid of the Moon to the Pyramid of the Sun is not an occasion for quiet contemplation, but of running a gantlet of some of the most persistent vendors anywhere in Mexico. Selling jewelry, blankets, obsidian carvings, clay flutes and brass plates, they're reluctant to take "no, gracias" for an answer.
Tours to the pyramids, with English-speaking guides, can be arranged by most hotels and are likely to cost about $20.
It's also possible to get to the ruins by bus, or even by taxi, but most visitors opt for the tour buses. One advantage is learning a little history on the way; one disadvantage is not being able to take your time at the ruins.
On a tour, the first stop may not be the pyramids, but a store and factory where chunks of black volcanic obsidian glass are carved into reproductions of art objects from throughout the region. If the tour driver seems particularly interested in showing the fine detail of obsidian carvings, be aware that he probably is getting a commission on the purchase.
The Teotihuacan archaeological zone is open daily from 9 a.m. to p.m. The best time for photographs is usually in the fading late-afternoon light or just before sunset.