Into the volcano: crater walking on Nevado de Toluca offers high-altitude sightseeing.

Getting away often means changing the scenery: giving your eye an unaccustomed vista, witnessing new geographical features, measuring distances in an unfamiliar way. By that standard, Nevado de Toluca makes a superior getaway. With its pair of emerald, mirror-surfaced lagoons and red-streaked crater rim, Nevado more closely resembles the surface of Mars than the streets of Mexico City or Monterrey.

Yet unlike its taller siblings, Orizaba, Popocatepetl and Iztaccihuatl, Mexico's fourth-tallest peak is relatively easily scaled, with a road leading right into the crater of the extinct volcano.

Nevado de Toluca's last eruptive period took place some 30,000 years ago, concluding when a lava dome sealed the open cauldron. Precipitation filled the double bowl that remained, forming the two lagoons now called Sun and Moon, which are among the world's highest bodies of water. Dubbed Chicnauhtecatl (nine hills) by pre-Hispanic inhabitants, the volcano probably served a religious function. Bits of copal (a fragrant resin used as incense) and fragments of painted pottery have been found within the crater.

The volcano is a prominent feature of the landscape southwest of Toluca. As you head west from the city, its truncated cone, shrouded in clouds, towers above flat cornfields. After a barely marked left turn, the road to Sultepec heads for the volcano. Take another sudden left at the village of Raices and you'll leave the pavement to ascend the lower slopes.

The entrance to Parque Nacional Nevado de Toluca is four kilometers ahead at a recreational area called Parque Los Venados. Here you pay the 10-peso entry fee and begin the 17-kilometer ascent of the volcano's northern slopes. It's slow going along the rocky, rutted twisting road to the summit. Depending on the roadworthiness of your vehicle, it can take up to an hour. Purple lupines line the roadside, and conifer forests give way to scrub and papery thistle. You'll know you've arrived when the road levels off and you see a few small buildings ahead. One of these is the humble Posada Familiar with basic accommodations at 50 pesos per person.

GETTING HIGH

At over 4,000 meters the air has a wintry chill, and physical exertion is difficult, especially for those unaccustomed to strenuous exercise. Just standing up can increase your heart rate. The climate is notoriously variable: one moment, gray clouds are scooting past, releasing hail or snow, but then the sun breaks through and shines bright. Be sure to pack a few layers of clothing and sunscreen and drink more water than your thirst dictates.

From this point there are two paths to enter the crater: by driving (or better yet, cycling) another five kilometers around its outer edge on a level road or by climbing over a short rise. Taking the latter route, you can descend to either of the two lagoons. The Laguna del Sol is a long crescent-shaped body of deep green water. A coarse sand beach strewn with volcanic boulders skirts the bank, rising toward the steep, craggy walls of the crater rim streaked with veins of red and white pumice. Separated from its partner by the lava dome is the smaller Laguna de la Luna, a navel-like depression with clear waters that shift in hue throughout the day, mirroring the dome and obliging visitors to reach for their cameras.

On weekends, families congregate at the road end of the Sun Lagoon to picnic, hike or simply admire the panorama. Intrepid climbers scale the sandy surface of the north rim to reach the 4580-meter Pico de Aguila then hike along the ridge to the slightly higher Pico del Fraile, though the ascent to the latter includes some treacherous scrambles over boulders.

They're rewarded with astonishing glimpses of the crater and, on a clear day, panoramic views of the Valley of Toluca to the north and the sentinels of Popo and Izta to the east. However you choose to explore Nevado de Toluca, the experience is sure to refresh your perspective.

Daniel C. Schechter is a freelance travel writer and Lonely Planet author.