The San Diego Zoo is certainly one of the best in the world. For the past 75 years, it has been the model for progressive zoos everywhere. It’s an inspiration for others to transform their practice from confining animals in cages to allowing them the freedom to roam through expansive natural living areas.

We seniors recall childhood zoo visits, where there were only barred cage after cage of listless animals. Yesterday's zoos were prisons, where inmates endured life sentences of endless boredom, lack of companionship and minimal exercise.

One of the most heartwarming aspects of the San Diego Zoo is that it's designed to allow animals to live as naturally as possible, with plenty of space for interacting with their own species and other compatible animals. At the same time, the zoo invites visitors of all ages to find interesting areas to stop and observe without disturbing the animals. Not at this zoo does Dad say to the children, "Let's go and laugh at the monkeys in their cages."

The San Diego Zoo and surrounding botanical gardens cover a vast 80 acres in the city’s downtown. Among the expansive animal compounds are species of plants and trees from around the world. All are designed for both aesthetic beauty and to provide natural places for the animals to roam freely.

Some trees, including coconut palm and various fruit, also provide foods for primates and other animals. Visitors can feel they're in completely natural surroundings at almost any place in the zoo. There are more than 4,000 zoo residents, including endangered animals.

Also residing there are various wild cat species, elephants, hippos, zebras, anteaters, meercats, exotic birds, dragonlike lizards, tiny deer and hundreds of other species.

The fun and wonder begin immediately after visitors pass through the zoo entrance at Flamingo Lagoon. There's a large flock of the tall, brilliant pink birds placidly wading and grooming.

After strolling around the lagoon, enter one of several tropical forest areas, where exhibits include both harmless and poisonous snakes, as well as many exotic birds and species of rare monkeys that inhabit the forest's trees.

Seniors should be aware that considerable walking is required for a full zoo experience. For seniors and others who need it, there’s a hop-on-and-off shuttle that moves throughout the park. There are also two express shuttles that offer quick rides to certain popular areas, such as the panda and polar bear exhibits.

Another unique way to see the zoo is from above on the Skyfari Aerial Tram, which zooms along just over all the zoo exhibits. It also allows passengers some great views of downtown San Diego and the surrounding ocean harbor.

The address is 2920 Zoo Drive. In summer daylight savings time, it's open daily from 9 am to 8 pm; the rest of the year from 9 am to 4 pm. For current ticket prices and other info, call 619-234-1515 or email www.sandiegozoo.org