Why fly to London to climb the narrow staircase in the Tower of London when you can huff and puff your way up the 898 steps of the Washington Monument?

Being a tourist in your own city is a great deal cheaper than exploring Marrakesh, even if you charter a minibus and take along a party of friends.

Although many of the charter tour buses provide guides, you could also write your own commentary. Look up old guide books in the Library of Congress, the Wasshingtoniana Division of the Martin Luther King Library or the Columbia Historical Society. Or buy a book like "The City of Washington, An Illustrated History," for historical sidelights on our public buildings.

Most guides will tell you the Washington Monument is 555 feet and some inches tall, but did you know it took almost 40 years to get the thing up? Among the difficulties was the theft in 1848 of a marble block, a gift from Pope Pius IX, by members of the American Party (the anti-Catholic, anti-immigrant Know Nothings), who later engineered a takeover of the Monument Society, effectively stopping both congressional funding and public subscription.

Or that when the original Library of Congress burned down in 1814, Thomas Jefferson sold his own 6,000-book collection to the Library for $23,950?

And when the Executive Office Building was completed in 1887, "the largest granite structure in the world" was viewed by a prescient newspaperman, Frank Carpenter, who wrote "As I stand here on this marble pavement and think of the lives that will be eaten up in this building, and of the enterprise shriveled into inertia, it makes me shudder."

Since touring is a tiring business, pack a lunch of monumental sandwiches, and make a pre-tour raid on a souvenir store so that each of you guests will receive a memento -- a plastic replica of the Capitol, or perhaps a plate bearing a picture of Jimmy Carter.

International Limousine Service (232-6992) rents a 14-passenger minibus for a four-hour tour of Washington's monuments. They charge $24 an hour and will pick up and deliver your group.

Minibus Limousine Service (635-8653) has minibuses for 14 to 19 passengers. The smaller bus rents for $20 an hour for a four-hour tour of Washington.

If you still haven't given up the idea of going to London, rent a London double-decker bus for your tour.

Spirit of '76 (529-2575) will drive you around the city for $37.50 an hour with a four-hour minimum.

White House Sightseeing Tours (393-1616) will provide a 47-person private coach, air conditioned and with its own restroom and p.a. system for a variety of different tours around the area. Least expensive is their four-hour tour of Washington landmarks, which is $8.80 a person with a 35-person minimum.They also pick up and deliver groups within Washington.