Imagine there's a vacant lot next door to you. Behind a high fence, there's construction going on. Then one day, a moving van pulls up with your new neighbor - an animal. What will the house look like?

When architect Nancy Renfro presented this problem to a group of kids, they came up with some amazing solutions. An alligator's house had waves lapping at the windows. An eagle's house had a supply of live mice in the basement. A giraffe's house had trees on the roof which the inhabitant could nibble through a skylight.

"If I just asked the kids to draw a house, they'd draw the conventional symbol of a house - a box with smoke coming out of the chimney and a picket fence," said Renfro. To get kids to look beyond such conventions, Renfro asked them to design houses for animal clients, or houses you can carry on your back, or secret hideaways, or stores for kids only. Sponsored by the National Endowment for the Arts and the Smithsonian Institution, Renfro's workshops were conducted for children from 7 to 12 in Pennsylvania schools and at the Smithsonian.Some of the results are displayed in an exhibit entitled "Kids As Architects," at the Renwick Gallery through July 30.

When Renfro asked the students to design houses they could carry around with them, they drew a bubble-topped wheelchair, a "snug-a-bug" house that was a synthesis of a turtle sheel and a snail shell to be carried on a cushion on top of the owner's head, and a renovated rollerdrum pulled by a bicycle. Perhaps the most ingenious was a bouncing doghouse equipped with an air compressor that continually blew up balloons on the roof and then let the air out again. When the air was let out, the house came down - but softly since it was mounted on springs. (Eat your heart out, Snoopy.)

The "energy" houses could be powered by sun, water or air. One, a sunflower-shaped house, turns to follow the sun all day. One had a water-catcher on the roof that doubled a swimming pool. Another had air blowing through the house, cooling the occupant and fueling the lights.

There was only one rule about the restaurant designs: they couldn't have a golden arch. "Kids love McDonald's," said Renfro. "But I thought they'd also enjoy competing without trying to knock it out of the top place." One potential competitor was "Sharkies," which customers would enter through classic jaws. Sinbad's Seafood invited customers to "get hooked on Seafood" and dispensed meals through shoots in the walls.

When Renfro had kids pair up and design secret hideaways for two, these devious young imaginations went wild. They created underground twin towers in the shape of King Kong. They designed a hideaway in the shape of a magician's hat - to which the congnescenti gained entrance by pulling the rabbit's ears. An underwater hideout was in the shape of a fish. Trespassers into one hideaway landed in a beehive, and anyone trying to get into another hideaway would be automatically crushed by a 200-pound weight. For the elect, however, the hideaways held everything a young heart could desire, including self-replacing refrigerators and faucets that dispense soft drinks instead of water.

Some of these ideas, said Renfro, are practical possibilities. "For instance, I would love it if we all had those bubble-topped wheelchairs. I'd love to see those rolling along the streets."

Would a kid design an ugly glass box of an office building and carve it into cubby holes called offices? Not according to Renfro, who believes kids have a natural bent for creating "happy places."

If they're turned on to architecture at an early age, said Renfro, some of these kids might grow up to become architects who "use modern technology to create a more personal environment."