The Philadelphia Zoo, opened in 1874, was the nation's first. Today, the 42-acre zoo tucked into West Fairmount Park has become a national leader, with nearly 1,800 animals. The zoo celebrated its 125th anniversary with the opening of the PECO Primate Reserve, a breathtaking pavilion that blurs the line between visitors and its 11 resident species. Note that the basic admission (in season $17 for adults, $14 for children) does not include a lot of special attractions like the Zooballoon, a 15-minute ascent on a helium balloon that goes 400 feet high.

The 1 1/2-acre Carnivore Kingdom houses snow leopards and jaguars, but the biggest attraction is the rare white lions. Feeding time is around 11am for smaller carnivores, 3pm for tigers and lions. The monkeys have a new home on four naturally planted islands, where a variety of primate species live together naturally.

In the magical Jungle Bird Walk, you can walk among free-flying birds. Glass enclosures have been replaced with wire mesh so that the birds' songs can now be heard from both sides. The Treehouse ($1 extra) contains six larger-than-life habitats for kids of all ages to explore -- oversize eggs to "hatch" from, an oversize honeycomb to crawl through, and a four-story ficus tree to climb and see life from a bird's-eye view. The very popular Camel Rides start next to the Treehouse. A Children's Zoo portion of the gardens lets your kids pet and feed some baby zoo and farm animals; this closes 30 minutes before the rest of the zoo.

Other exhibits include polar bears; the renovated Reptile House, which bathes its snakes and tortoises with simulated tropical thunderstorms; and cavorting antelopes, zebras, and giraffes that coexist in the African Plains exhibit.

A tip for those who are driving here:  Try to arrive early in the day; it's a long hike from the more distant lots if you don't.