Humans have an insatiable fascination with wild animals. Every year, millions of people go on safaris, board whale-watching cruises and watch Jeff Corwin get attacked by snakes on Animal Planet; others drive to their local zoo for a full day of animal gazing.

This interest in animals is nothing new: Zoos have been entertaining people with exotic animal collections as far back as 1250 B.C. [source: Fravel]. Later, in early 13th-century England, Henry III moved his family's royal menagerie to the Tower of London for public viewing. For a small fee, visitors would be treated to glimpses of animals like lions, camels and lynxes. And if they brought a dog or cat to feed the lions, they got in for free [source: Encarta].

The first modern zoo -- the Imperial Menagerie in Vienna, Austria -- was established in 1752 and continues to attract visitors to this day. Nearby, in Germany, is the world's largest animal collection: Zoo Berlin (formerly The Berlin Zoological Gardens) houses more than 15,000 animals from almost 1,700 species [source: Encarta].

All U.S. animal exhibitors, like the 265-acre (107-hectare) Bronx Zoo just a subway ride away from Fifth Avenue, must apply for and receive a license from the Department of Agriculture. Millions of people visit the thousands of zoos around the world, proving that we simply never grow tired of observing wildlife.

Depending on your point of view, though, zoos are either sanctuaries of education and entertainment or unnecessary prisons. While some people argue that zoos play an important role in conservation and research, others counter that they do more harm than good.

So which is it? Are zoos good or bad? And how do you differentiate between what's good for one animal versus what's good for the entire species? It's a delicate question and one that can't easily be answered. Let's start with the good news.