It looks like a case of landscape schizophrenia. In one direction, the country appears as savage as the most parched and desolate corner of Arizona. Vicious crags slash the sky, some slopes brandishing daggers of splintered palisades. Gangs of volcanic monoliths make wild stabs at the cerulean heavens. This is a wanton desert where vultures soar, snakes strike and cacti raise arms in futile surrender.

Face the opposite way and the temperament changes. The wilderness calms to the lull of sandy beaches and a sea, tranquil as Valium. Placid waves caress the shore, and breezes waft the soothing scent of saltwater. Captured in this split personality of desert and ocean lies San Carlos, one of Mexico's least crowded beach resorts.Located 310 driving miles south of Tucson or an hour's flight from Phoenix, San Carlos sits near Guaymas along the Gulf of California. Its subtropical latitude approximates that of Tampa and Corpus Christi. Winter temperatures approach the 70s, and in summer they can reach triple digits. Rain is rare.

Unlike Mexico's parrot-and-palm-tree resorts, San Carlos does not entertain the Love Boat crowd. There are no cliff divers, tours to Mesoamerican ruins or parasailing from hotel beaches. The town of 6,000 may not even have a year-round, all-night disco. Instead of glitz, San Carlos offers sun, sand and solitude spread along miles of coastline.

The first view of San Carlos can be misleading. The highway from Guaymas enters town through a strip of RV parks, motels, restaurants, bars and trinket emporiums. Vacant land lies in weeds, often covered with debris. It mimics the poor side of anywhere.

A side street leads to the marina. Between roadway and water sits the Plaza Las Glorias, a combination luxury hotel and adjoining timeshare condo. Built as a high-rise pueblo, it towers like a stack of decorative boxes, each sporting its own bay-watching balcony. From high up, guests gaze out to a harbor squeezed between the twisted pincers of two stony peninsulas.

A brick walkway separates the hotel from the bay. A handful of shops and restaurants lines its course. Beneath sidewalk canopies, visitors dine on Sonoran cuisine rich in seafood. Others just relax and stare beyond the yacht masts to contemplate a looming Tetakawi.

Symbol of San Carlos, the twin-topped volcanic plug juts a thousand feet above the sea, its devilish horns protruding from a triangular skull. Dark and ominous, Tetakawi overlooks the bay like a pagan deity searching for sacrificial virgins.

On the near peninsula opposite Tetakawi, cobblestone streets access the whitewashed homes that cling like lint to the brown hillside. Bougainvillea climb their arched porticos, and imported palms reach for red-tiled roofs. Most of the junior haciendas have patios overlooking the water. Some face the San Carlos Bay Marina. Others look to fishing boats plying the open sea.

The Guaymas Trench gouges the nearby ocean floor. Deep as the Grand Canyon, the underwater abyss provides the area with some of the West's finest sport fishing. In winter anglers hook grouper, yellowtail, barracuda and red snapper. The warmer water of summer brings marlin, bonita, sailfish and corivina. In July, the area hosts an international deep-sea fishing competition.

For landlubbers who prefer clubs to poles, the San Carlos Bay Country Club offers an 18-hole golf course that is open to the public. The links feature fairways lined with cactus and offer unencumbered views of desert and sea.

Not long ago, these barren expanses were nothing but a sprawling cattle ranch. With the death of its owner, the estate was broken into smaller tracts. In the 1960s, Sonoran businessman Rafael Caballero bought a few parcels and began developing a resort community. He hoped it would attract some of the chill-chased folks who annually flee from the Snowbelt.

Caballero soon discovered that San Carlos, one of Mexico's northernmost major resorts, enjoys two peak seasons. Winter may bring the snowbirds, but summer has proven to be busiest with hotels brim-full of vacationing Mexicans. Spring and fall remain uncrowded and relaxed.

Regardless of season, those who want to sample a variety of restaurants and bars stay in the main part of town. Others who crave isolation continue down the highway to the far side of Tetakawi.

The road passes the Royal Marina, another moorage filled with motorboats and yachts from all over the West. Beyond is the pink and beige bulk of the San Carlos Plaza.

The 173-room hotel is ideal for those who want their vacation needs met in one self-contained property.

The structure features marble floors and a fountained atrium lined with a few shops, bars and restaurants. One offers strolling Mariachis to entertain at dinner. A brick deck outside surrounds twin pools and a hot-tub spa. Close by, a thatched-roof bar often features live music. A strip of beach beyond separates the hotel from the ocean. In winter, the water may be a bit nippy for swimming.

A mile of arcing beach stretches northward from the San Carlos Plaza. The locals call it Playa Algodones, Cotton Beach, named for its light sands that drift into 30-foot-high dunes. It was near here that Mike Nichols filmed "Catch-22."

In the film, the barren countryside depicted a World War II bomber base in the Mediterranean. Portions of the set's rock walls remain, now outlining roofless rooms. Arched doorways lead to empty expanses. The movie's airfield has been trenched to prevent its use by contraband-ferrying pilots.

Near where the runway reached the shore, Mexican families now enjoy a public-access section of beach. On a warm day, blankets cover the ground and canvas tarps hang from makeshift frames to form lean-to shelters. Children dig in the damp sand, teens toss Frisbees and adults sit and sip in the shade. Boom boxes entertain the crowd with Mexican rock-and-roll. Unlike resort beaches that are cleaned daily, litter here unfortunately lies everywhere.

At day's end, the air cools as the sun sinks to the sea. Canopies and chairs stand silently empty, abandoned by guests who have departed for dinner. The cloudless sky darkens, its seamless hues mutating from blue to yellow and on to blushing pink.

Cast in shadow, the surrounding desert loses its sinister countenance. Mountains become dusky shapes, and cacti blacken into Rorschach-test blots on the luminous horizon. Even Tetakawi, its silhouette diminished in darkness, seems less omnipotent.

In the sedative of evening, the landscape's divergent personalities merge. Earth and ocean unite into the halcyon serenity of San Carlos.

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ADDITIONAL INFORMATION

If you go

When to go: The desert climate of San Carlos is tempered by its proximity to the Gulf of California. Winter temperatures average about 70 degrees, with summers heading into the mid-90s. Spring and fall are ideal. In the cooler months, San Carlos attracts American and Canadian snowbirds. Summers are more crowded with vacationing Mexicans. Unlike most tropical resorts, many establishments consider winter to be the low season, and often discounted accommodations and package rates may be obtained.

Getting there: Aero Mexico (1-800-237-6639) serves Guaymas with nonstop jet service from Phoenix. Their subsidiary, Aerolitoral, provides turboprop flights from Tucson, Ariz. Connections are available from other U.S. and Mexican cities.

By car, San Carlos is 250 miles south of Nogales, Ariz., on Mexico Route 15, a divided toll road similar to our interstate highways. Mexican auto insurance is necessary. Sanborn's Mexican Insurance Service (210-686-0711) can arrange coverage and provides a detailed "Mexico Travelog" with mile-by-mile route information.

Drivers must bring their vehicle title, registration card or lease contract.Call 1-800-4SONORA for details.

Traveling to Mexico: U.S. and Canadian travelers must bring proof of citizenship. Best is a current passport, but a certified copy of a birth certificate and photo identification may be used. Upon entering Mexico, immigration officials issue a tourist card, which should be carried at all times. Travelers should check with their local health departments to see if any immunizations are suggested or required.

Accommodations: Plaza las Glorias faces the marina in the heart of town, making it ideal for boaters or those who want to seek out what action San Carlos offers. The hotel features a restaurant and bar, and within easy walking distance are independent restaurants, bars and shops. Rates start at about $150. Call 1-800-342-ANUGO for reservations.

For more information: Call Mexico Tourism at 1-800-446-3942 or Sonoran Tourism at 1-800-4SONORA.