THE FIRST IMPRESSION is that it's an exotic new version of Alice's wonderland.

Visitors are greeted with a view of science fiction-sized aquatic plants and sensationally colored Koi (Japanese carp) that grow up to 30 inches in length and 30 pounds. And it gets curiouser.

Our family had come to see the National Arboretum on a warm early fall afternoon, not an exciting-sounding outing for kids who would rather be hanging out, poking holes in screendoors or carving their initials on their brand-new bunkbeds.

But a drive through the spectacular grounds reveals an eye-catching view or magnificent display at every turn.

We marveled at the vertical rows of flowers in the American Country Garden. Normally these species spread out along the ground, but this display is dedicated to showing people how to make a lovely garden that grows straight up, appropriate for limited, urban space.

"It's like the Mad Hatter's tea party where everything's topsy-turvy," I told the children.

Unlike the tea party, where the Hatter, March Hare and Dormouse were all crowded into one corner of the table, this 444-acre plant museum has a lot of stretching space.

We concentrated on just one section of the Arboretum: the pool, the bonsai trees and the National Herb Garden. Most exciting to the children were the fish.

"They're huge," yelped bugeyed Adam, 7.

"They're so many colors!" piped up Ben, 5.

"They're going to bite me," whimpered Emily, 3. (Well, maybe gum her. They have no teeth).

Indeed, the Koi, eager for their daily noon feeding, were thrashing and sliding over each other, mouths agape.

"They think we're going to feed them," said Adam. It turned out they were right. The gardeners invite visitors to scatter the food. We fed "Jaws," the 80-year-old oversized granddaddy of the pond. "He's so imposing he reminds me of the fish-footman in Alice in Wonderland," I said. He was the one who delivered an invitation for croquet from the Red Queen to the Duchess.

The Koi reside in a pond filled with three-foot Victoria lily pads. Erik Neumann, head of education and public services for the Arboretum, said the plants' heavy veins and roots are strong enough to support a small child.

The four-inch blossoms contribute to the feeling of unreality.

"It's as if we had drunk from Alice's mysterious bottle labeled 'Drink Me' and have become three inches tall," I said.

But if you really want to feel as though you've stepped through the Looking Glass, walk next door down a cool avenue of normal-looking trees to the bonsai collection of miniature trees.

"Now," I said, "I feel like I've eaten a bit of magic mushroom and have grown 10 times my normal size."

The trees are lush and beautiful, up to 360 years old, and make their homes in pots.

"They're dollhouse trees," said Ben.

"They can't be trees," scoffed Adam. "If you climbed one, you'd be sitting on top of it."

"They are real trees, Adam," said his dad, attempting to make contact with reality. "This one {he pointed to the gingko} was planted before the Civil War. Its roots were pruned to control its growth so it could continue to grow in a pot."

"This one," I said, showing him a 260-year-old Needle Juniper, "was planted before the Revolutionary War. And the oldest of all, the 360-year-old Japanese White Pine, was planted when the main inhabitants of the United States were Indians and buffalos."

"Are these trees older than our old wreck?" asked Ben, referring to the family car.

We crossed the road to the National Herb Garden, a circle of specialty gardens that beckon and entice with their smells, blossoms and brightly colored insects.

The herb gardens include Discorides' (he was the father of pharmacology) in which grow such things as marshmallow, anise and chamomile, Early American and American Indian, Fragrance, Oriental, Culinary and Industrial, Dye and, finally, the Beverage Garden, which includes coffee and cocoa.

Seeing these gardens, reading the names and sniffing the scents, reminds children that they are hungry. If you've been smart enough to bring a picnic lunch, this is the time for it.

Included in the herb complex is a Knot Garden composed of dwarf evergreens grown in a series of interlinking chains, and the 50- by 80-foot Historic Rose Garden. The roses bloom in June and early July.

"I'd like to come back next summer to see whether we will find playing-card gardeners painting the roses red," I said.

"I want to come back to see if 'Jaws' is still here," Adam replied.

I thought my "Alice" references were wasted until Adam looked up from reading the Arboretum map.

"I'd like to visit Dogwood Circle," he said. "To see if they bark."

The brilliant color of blossoms comes to the Arboretum in the spring, but fall visitors will see brightly colored leaves.

The Country Garden and New American Garden are very nice up until frost, Neumann says, and the crabapples, boxwoods and hollies are good through the fall. The bonsai are good anytime, he notes, and the Koi stay in the pond all year, though they stay low in the water during the winter months.

To get to the Arboretum, exit the Beltway at U.S. 50 west, which becomes New York Avenue. At the first intersection turn left onto Bladensburg Road, go three blocks, then turn left on R Street and drive 300 yards to the entrance.

You'll think you fell down the rabbit hole.