JUST ABOUT EVERYONE and his cousin from Peoria seems to have visited the U.S. Capitol -- it's a fixture of capital life. But like an old friend you take for granted, the Capitol can offer a surprise or two.

For instance, did you know that Capitol Hill was originally named Jenkin's Hill -- for the farmer who tilled its soil? That the Capitol was once more like a rowdy street market than a seat of government? (What's that? -- you say it still is?) And that the statue that looks like an Indian atop the dome isn't? Read on and pick up a few lesser-known facts to impress your next contingent of out-of-towners.

To capture what the Capitol was like in the early days, in the first decade of the 19th century, enter from the East Front, through the center doors under the main stairs. Just to the right is the recently restored Old Supreme Court Chamber. Originally, the Court and both houses of Congress were housed in the two old wings adjacent to the Rotunda. The "new" House and Senate wings were added in 1857 and 1859.

To the west, just outside the court chamber, a narrow spiral staircase leads up to the main floor. Down the hallway to the right is the Old Senate Chamber, recently restored to its ancient splendor using an 1842 print of a late-night session showing Webster, Clay and Calhoun debating.

Over in the newer Senate wing, you'll find one of the most impressive chandeliers in the Capitol in Room S-211. It originally hung in the East Room of the White House, but Mrs. Teddy Roosevelt was bothered by the clinking of the glass and had it sold to the Capitol. Mrs. Kennedy thought of reinstating it in the White House, even though it was a tad large for her taste. She had it taken apart to see if it could be made smaller but it couldn't so it was returned to the Capitol.

The slightly overwhelming decoration of the Senate corridors is part of an elaborate decorative scheme developed by Constantino Brumidi. But if you look closely amid all the antique artwork on the ceiling on the north corridor near the Democratic Policy Committee room, you'll see astronauts walking on the moon. The moon walkers were contributed by Allyn Cox, who has done much of the contemporary art in the Capitol, including the painting of Washington laying the cornerstone on September 18, 1793 (in the first-floor corridor in the new House wing).

Today everyone can appreciate the august dignity of the mighty Rotunda just south of the Old Senate Chamber, but it was not always thus. In the early days of the Republic, vendors hawked their wares here, selling all manner of souvenirs and food. There was a time when the House restaurant served spirits and the Senate did not, and you could see parched Senators scurrying across the Rotunda to imbibe, particularly during late-night sessions.

The rotunda gained its due respect only after the addition of the new legislative wings shooed out the money changers, petitioners and office-seekers and after it was crowned by its mighty dome during the Civil War. Designed by Thomas Walter, the dome is a modern engineering feat. It's really two metal domes, the unseen inner one supporting the one we see. Congressmen can make arrangements with the Architect of the Capitol or the Capitol Historical Society to tour the dome with their honored guests. A narrow staircase, barely visible from the Rotunda floor, winds its way up to a little balcony at the very top of the dome. Almost all visitors experience vertigo as the world slips out from beneath them.

Visitors lucky enough to be invited on one of these tours can go outside at the very top of the dome. From here, the simple beauty of L'Enfant's plan is obvious as the wide avenues radiate out from this focal point.

Just above, you can catch a close-up view of "Freedom," Thomas Crawford's 1856 statue gracing the top of the dome. It's the allegorical figure of a woman in flowing draperies with a helmet of feathers inspired by Indian headdress. She originally wore a liberty cap derived from classical models, but it was changed when Secretary of War Jefferson Davis, objected, arguing that this would inflame passions over slavery.

To the south of the Rotunda is Statuary Hall, the original House Chamber where U.S. representatives met for 50 years and now the repository of two statues of notable people from each state. It has been partially restored to reflect its old spirit, but since it's a major tourist corridor, it can't be fully renovated. Heavy curtains such as the ones hanging there today, were hung to deaden unwanted noise, even though a convenient echo let the Democrats eavesdrop on Whig caucuses. (A small brown disk marks the spot where you can hear a conversation clear across the room.)

Note the gilded statue of King Kamehameha, first king of Hawaii, who united his nation by inviting all the other chiefs to a banquet, drugging their drinks and having them all murdered.

Having spent the morning wandering the halls of Congress, you'll be ready to leave the building and enjoy the grounds. The best way out is to walk around the House Chamber to the left and go down the stairs to the ground floor.

Since the early 1900s, 94 memorial and historic trees have been planted on the Capitol grounds; 73 are still living. The oldest surviving tree is the big American elm at the southeast corner of the new House wing, planted in the mid-1800s in memory of Senator Simon D. Cameron of Pennsylvania.

From the West Front of the Capitol, visitors can take in one of the most beautiful panoramas in the United States -- from the Jefferson Memorial to the White House, from the Smithsonian Institution to the Lincoln Memorial. In the distance, you can even catch the National Cathedral.

And if you look up to the roof over the Old House Chamber, you'll see a sqat little flagpole. We've all seen flags flying proudly over the Capitol. But when a Congressman offers his constituents a flag certified to have flown over the Capitol, it's done here. Men from the Architect of the Capitol's office regularly climb up on this roof and madly yank flags up and down.

If you're smart, you'll have brought your own lunch and you can head down the West Terrace steps and north across the lawn in front of the U.S. Grant Memorial. To the northwest and southwest in front of each Capitol chamber, you may notice two granite silo-like towers. They were part of an early effort to air-condition the chambers but increased the humidity so much that they turned the Capitol interior into a steambath.

Just in front of the new Senate wing, you'll find a charming three-sided, 19th-century trolley stop. Made of red brick with a partial tile roof, it's open in the middle and the little waterfall is in fact the underground Tiber Creek. This is a great place to rest and enjoy a brown-bag lunch.

No visit to the Capitol is quite complete without a stop at the beautiful U.S. Botanic Garden at the bottom of Capitol Hill, at the corner of Independence and Second Street SW. The permanent indoor garden is magnificent, but there are also regular seasonal shows. And from here, you can gaze back at the Capitol rising majestically -- and picturesquely -- from amongst the cherry trees and evergreens. TAKING INTEREST FROM THE CAPITOL

The Capitol is open 9 to 4 daily. Guided tours operate continuously during those hours. Call 225-6827 for guided-tour information.