Arlington National Cemetery is a surprisingly good place to spend several interesting hours very inexpensively. For only $2, Tourmobile offers public tours.

The tour begins not far from the cemetery's front gates. There's a subway stop about six blocks away or, if you're driving, there's free two-hour parking in a nearby lot. An articulated bus slowly carries its passengers over the winding drives named after historical personalities and events. Guides immersed in the history of the grounds and its ocencupants narrate as the bus goes along. The guides are "encouraged to do research on their own and keep it (the tour) from being a bunch of disjointed facts -- keep it interesting," according to Eileen Andary, vice-president of personnel at Tourmobile Sightseeing.

Guides can emphasize certains aspects of the tour that they find particularly interesting, but everything is checked against history to prevent embellishment. They take questions and usually can answer them.

The tour takes 30 minutes or, if you get off at all three stops, an hour and 20 minutes or more.

At the Tomb of the Unknown Soldier, the guard is changed on the hour and there's always a crowd. Long after they've gone, the Army soldier continues his "walk" through the night despite the weather.

"I love it! It's a challenge and it gets harder each walk," said Gerry Mansell, 28, of State College, Pennsylvannia. "It's one of the highest honors an enlisted man can have."

The guards serve 24 hours on and 48 off, with each guarding the tomb for an hour at a time, several times per shift. His head must be cocked back, chest out and back straight. Mansell admits there's a lot of pain in the job; the average tour of duty is two years.

The next stop is the Custis-Lee Mansion. Private William Christman of Pennsylvania, who died from peritonitis on May 13, 1864, was the first Civil War soldier to be buried on the grounds of the Confederate commander's home, seized by Union troops. Many thousands more followed, both blue and gray.

George Washington Parke Custis, adopted son of the first president, built the Greek Revival home on 1,100 acres of rolling farmland and forest in the early 1800s. Upon his death in 1857, Arlington House and its estate became the possession of his daughter, Mary Randolph Custis. She and her husband, Robert E. Lee, raised their children in the seven-bedroom mansion.

A month after war broke out, Mrs. Lee collected the family and eight wagonloads of belongings and fled as Union troops moved across the Potomac. In those days, property taxes had to be paid in person, hard for a family at war against the United States. In 1864 the government claimed the property in lieu of $92.07 and set aside 200 acres for a national cemetery. An 1883 Supreme Court decision returned the property to the Lees, who sold it back to the government.

Since Christman's burial, 186,000 veterans of American wars and their dependents -- including 11 veterans of the American Revolution who were reburied at the turn of the century -- have been laid to rest on 572 acres. Another 40 acres await use; cemetery officials expect to reach capacity by the year 2020 at the present rate of 12 to 15 funerals per day, Monday through Friday.

The final stop is at the graves of President John F. Kennedy and his brother, Robert F. Kennedy.

Other graves along the route include those of Oliver Wendell Holmes Jr. and William O. Douglas, associate Supreme Court justices; Daniel "Chappie" James Jr., first black four-star general; Audie Murphy, most-decorated U.S. soldier of World War II and later a Hollywood star; prizefighter Joe Louis; and Virgil Grissom and Roger Chaffee, two astronauts killed in 1967 when their spacecraft burned.

Three of the eight American soldiers killed in the attempt to rescue Americans held hostage in Iran are also here.

It seems only fittingi that Abner Doubleday should be buried at Arlington. Doubleday, better remembered as the alleged father of baseball, is said to have fired the first answering shot from Fort Sumter.

By special decree, President Franklin D. Roosevelt permitted the "temporary" interment at Arlington of Ignace Jan Paderewski, the Polish pianist-composer and president-in-exile, who died in 1941. There are no plans to move him; his heart, at his request, was buried in New York City. CEMETERY TOURS Buses leave every 15 minutes, every day of the year. The cemetery's winter hours are 8 to 5 (8 to 7 from April to September). The last bus leaves one hour before closing. For information on other Washington tours, call 554-7950..