A bit to the north of the city, these are an underground marvel, with chambers of spectacular formations, one the size of a football field. Gigantic towering columns, emerald pools, delicate, crystalline soda straws -- all living, still growing. During the summer, the first tour of the day is an exploration of the passages by the light of cave lanterns, just as students who first discovered the place in 1960 saw it. Basic tours cost around $18 and take 70 minutes. An adventure tour with caving gear can take up to 4 hours and cost around $100.

The San Antonio River Walk is a public park with two miles of walkways, open every day of the year, lined with restaurants, hotel, and other attractions. Events here include canoe races and an August Lucky Duck Race & Festival, with food, music, and 10,000 rubber ducks racing through the water. You can get out on the water too: Rio San Antonio Cruises has 35 minute narrated tours for $8 and change. They do dining tours, charters, and a river taxi service too.

The San Antonio Botanical Center includes the 33-acre San Antonio Botanical Garden and adjacent San Antonio Garden Center. Opened in 1980, this site was originally a 19th century limestone quarry, then an open reservoir, abandoned in 1899. Formal and display gardens change seasonally to display varieties of color and texture. The Lucile Halsell Conservatory has plants from desert regions to equatorial rainforests in climate-controlled glass buildings, tucked into the earth around a sunken courtyard and tropical lagoon. The Texas Native Trail showcases the flora of the Edwards Plateau, East Texas Piney Woods, and the South Texas region. Admission is $7.

Special events throughout the year include: Shakespeare in the Park in June; three summertime Concerts Under the Stars; plus walks, fireworks displays, galas, a jazz party, summer camps, and plant sales. See their website for the annual calendar.