Since mission times, the San Antonio River has been the key to the city's fortunes. Destructive floods in the 1920s, and subsequent oil drilling, reduced its flow, leading to plans to pave the river over. Instead, a careful landscaping scheme, started in 1939 by the WPA, created the Paseo del Rio, or River Walk , now the aesthetic and commercial focus of San Antonio. Below street level, the walk is reached by steps from various spots along the main roads and crossed by humpbacked stone bridges. Cobbled paths, lined with tropical plants and shaded by pine, cypress, oak and willow, wind for two and a half miles (twenty-one blocks) beside the jade-green water, with much of the city's eating and entertainment concentrated along the way. You can catch a river taxi at a number of places, but strolling is cheaper and just as much fun, for the view of the river slowly changing character between the lively Rivercenter Mall and the quieter, more park-like outskirts.

While the Alamo is the main attraction in the downtown area, the surreal Buckhorn Museum , 318 E Houston St (Sun-Thurs 10am-5pm, Fri & Sat 10am-6pm; $8.99), takes a pleasingly kitsch look at Americana. During San Antonio's heyday as a cowtown, cowboys, trappers and traders would bring their cattle horns to the original Buckhorn Saloon in exchange for a drink. The entire bar has been transplanted to this downtown location, which boasts an extra floor of exhibition space and, as well as thousands of horns on display, mounted as trophies, chandeliers and chairs, there are many stuffed animals, including "Blondie", an unforgettable two-headed lamb.

La Villita ("little town"), on the River Walk opposite Hemisfair Park, was San Antonio's original settlement, occupied in the mid- to late eighteenth century by Mexican "squatters" with no titles to the land. Only when its elevation enabled it to survive fierce floods in 1819 did this rude collection of stone and adobe buildings become suddenly respectable. It is now a National Historic District, turned over to a dubious "arts community" consisting mostly of overpriced craftshops (daily 10am-6pm). It's at its best off-season or at dusk, when the crowds dwindle and the muted colors, smells and noises are more evocative of earlier times. In contrast, the 25-block King William Historic District southwest, between the river and S St Mary's Street, contains the elegant late nineteenth-century homes of German merchants. A pleasant incongruity in this Mexican-feeling city, it remains a fashionable residential area and has some stylish B&Bs.

The best of several museums in HemisFair Park is the Institute of Texan Cultures , 801 S Bowie St (Tues-Sun 9am-5pm; $5), which maps the social histories of 26 diverse "Texan" cultures, with especially pertinent African-American and Native American sections, and an intriguing corner devoted to short-lived attempts to introduce the camel to West Texas as a beast of burden. The Mexican Cultural Institute (daily 10am-5pm; free) recently underwent a mammoth renovation, expanding into seven gallery spaces and a theatre, while retaining its focus on historic and contemporary Mexican art. The ugly 750ft Tower of the Americas is devoid of interest, save for the views from its observation deck (Sun-Thurs 9am-10 pm, Fri & Sat 9am-11pm; $3).

West of the river at 115 Main Plaza, the 1731 San Fernando Cathedral is the oldest cathedral in the US, though, contrary to the claims of the tourist board, nobody really believes that the Alamo heroes are buried here. Mariachi Masses are held on Saturday at 5.15pm, when crowds overflow onto the plaza. Two blocks west at 105 Plaza de Armas, the beautifully simple whitewashed Spanish Governors Palace (Mon-Sat 9am-5pm, Sun 10am-5pm; $1.50) was once home to Spanish officials during the mission era. Just one story tall, it's hardly a palace, but its flagstone floors, low doorways and beamed ceilings, religious icons and ornate wooden carvings give it a wonderful atmosphere, and it provides an illuminating glimpse of the lifestyles of the civil and religious authorities in this remote outpost. Don't miss the sweet cobbled courtyard, with its fountain, mosaic floor and lush palms.

Market Square (daily: summer 10am-8pm; rest of year 10am-6pm), a couple of blocks further northwest, dates from 1840. Its outdoor restaurants and bustle are still at the heart of the city's life; fruit and vegetables are on sale early in the morning, while the shops are a compelling mix of color and kitsch. El Mercado , an indoor complex, is meant to resemble a traditional Mexican market, selling tourist-oriented gifts, jewelry and oddities. A few of the shops are great, even if the air conditioning and piped music undermine the authenticity of the venture.

It's also worth getting to the beautiful McNay Art Museum , 6000 N New Braunfels Ave at Austin Highway (Tues-Sat 10am-5pm, Sun noon-5pm; free). This exquisite Moorish-style villa, complete with tranquil garden, was built in the 1950s to house the art collection of millionaire and folk artist Marion Koogler McNay, which includes modern sculpture, Gothic and medieval works, as well as a sprinkling of major players (Picasso, Monet and Van Gogh). Buses #11 (Nacogdoches) and #14 (Thousand Oaks) serve the museum from downtown. On the way there, bus #11 passes the San Antonio Museum of Art , 200 W Jones Ave (Tues 10am-9pm, Wed-Sat 10am-5pm, Sun noon-5pm; $5, free on Tues 3-9pm), which occupies the old Lone Star Brewery, but it's the added Rockefeller Center for Latin American Art wing that holds most interest, with its particularly fine exhibit on folk art.