San Diego Zoo100 acres in Balboa Park, 3,700 animals, the original cageless open-habitat zoo since 1916

The San Diego Zoo grew out of the 1915 Panama-California Exposition, when Dr. Harry Wegeforth incorporated the Zoological Society of San Diego in October 1916 around a few abandoned exhibition animals. Belle Benchley, the executive secretary turned director from 1925 to 1953, pioneered the open-habitat "mesa and canyon" design — replacing iron bars with moats and elevation — and established the wildlife conservation program that put San Diego on the global zoo map.

Today the 100-acre campus inside Balboa Park holds more than 3,700 animals from roughly 660 species and 700,000 plants from every major climate zone, organized into themed habitats: Africa Rocks (8 ecosystems including the only Cape fynbos exhibit in the US), Tiger Trail with Sumatran tigers, Lost Forest's lowland gorillas, Elephant Odyssey, the Children's Zoo, and the Conrad Prebys Polar Bear Plunge. The Skyfari aerial tram crosses the canyon at 170 feet between the front entrance and Polar Bear Plunge — included with admission and the easiest way to skip the climb back up.

Plan four to six hours for the full loop. Arrive at opening (9:00 AM) — animals are most active before mid-morning and before late-afternoon feeding — and ride the Guided Bus Tour first to map the layout. Free parking is in the front lot off Park Boulevard; nearby San Diego MTS Route 7 stops at the gate. Strollers and wheelchairs rent at the front for $14 / $30 / $30.