The best part of the Philadelphia Zoo's new KidZooU exhibit, at least in the eyes of my two nieces, was the barnyard. As the two stood in the exhibit, they were surrounded by colorful (goat) kids, all nuzzling them in an attempt to reach the brushes the girls held. A short distance away, they marveled over the sheep wandering in their pen. An extremely loud donkey - which made the girls think of Shrek - let it be known that he needed some attention.

Lest this sound like a typical children's petting zoo, realize this: KidZooU is all that you expect - and then a little more.

Take the sheep, for example. The zoo is featuring rare breeds, including Jacob sheep, each of which can have as many as six horns. (The pair we saw had four horns per sheep.) They're like no sheep we'd ever seen before.

And the exhibits, many of which are indoors, feature some animals you wouldn't expect to see on display. In one corner, rats - most of them jumbled in a pile while a few more adventuresome brethren ventured through a "gymnasium" - awaited their spotlight.

"Look! A mouse!" Fiona, 5, said as she pointed at the pile of rodents.

I didn't correct her. Then. But once the exhibit is in full force, she'll learn that rats are smart, clean, and make good pets, said Andy Baker, the zoo's chief operating officer. One goal of KidZooU is to take away the stigma tied to some animals like rats and pigeons.

"We hope children will leave the zoo, and, then when they encounter these animals in real life, they'll have a different relationship with them," Baker said.

Pigeons are also featured. The oft-maligned birds are smart, Baker said. They can count, and their homing skills - which will be showcased in warmer weather - are already known.

"People see them in city parks and have a negative opinion of them," he said. "This is bringing animals people think they know and see in their everyday lives and showing them through a different lens. It helps build respect and empathy."

Unlike the former Children's Zoo, which was tucked on the property's south end, KidZooU sprawls over two acres that include the former Pachyderm House, not far from the main entrance.

The indoor space means that, for the first time, the children's exhibit can have year-round programming. Much emphasis is on conservation and empowering children to be change agents, curator Marina Haynes said. They learn how simple behaviors like turning out unnecessary lights and recycling can make a difference to their animal friends.

"We see it as growing the next generation of environmental stewards," Haynes said. "There are a lot of things everybody, even children, can do on a daily basis to help animals . . .. We make it fun so they remember stuff and go home and repeat the behaviors."

Despite the name, KidZooU isn't just for youngsters, said Kristen Lewis-Waldron, the zoo's director of education. Designers approached the project so it would appeal to all age levels, with an emphasis on including those with special needs.

"This isn't a traditional children's zoo with a focus on kids under 5," Lewis-Waldron said. "We looked at those aged 1 to 12 as the specific target, but at the end of the day, it's a great place for the kid in all of us."

When I took Fiona and her sister Luna, 21/2, on a sneak preview trip to KidZooU a week before the official opening, much of the exhibition was still a work in progress. We could see the tower that would one day be filled with climbing goats - and the adjoining structure for climbing humans - but we couldn't try it out.

Our eyes followed the overhead mesh tunnel that would allow monkeys to visit from the Peco Primate Reserve, but the animals didn't make an appearance.

Though the girls were able to wander under the (artificial) giant ant welcoming visitors to the long-legged desert ant display, they weren't able to see the 2,000 ants in action - foraging for seeds, caring for their eggs, and paying homage to their queen.

But the brilliantly colored coral reef was ready to teach a lesson on ecology. The butterflies - hundreds of them - fluttered in their habitat. Australian parakeets clustered on a tree in their enclosure entranced Luna, who pressed her face to the glass.

The promise was there. And, I promised the girls, when the exhibit was finished, we would be, too.

KidZooU & You

What: The Hamilton Family Children's Zoo and Faris Family Education Center at the Philadelphia Zoo, 3400 W. Girard Ave.

Opening: April 13.

Info: 215-243-1100;

Outdoor features: Goat bridge and tower, pigeon loft, duck pond, rare animal breeds.

Indoor features: Rat gymnasium, ant habitat, tropical butterflies, coral reef fish.

Accessibility: KidZooU has stroller and wheelchair access.

Admission: KidZooU is included in the price of Philadelphia Zoo admission. Tickets can be purchased at the gate or online.

Tickets: Adults, $20; children 2 to 11, $18; under 2, free.

Parking: On zoo property, $15. Entrance and parking are free with zoo membership.EndText