SINCE 1963, when Fairfax County bought a one-third-scale replica of the steam-powered C.P. Huntington, nearly a million riders -- most of them children -- have entrained at Burke Lake Park for the 15-minute journey around a 1 1/2-mile track.

This Saturday, Burke Lake expects to honor that millionth rider -- a child, park manager Bob Grove hopes -- with a plaque, T-shirt, engineer's cap and coupons for free train and carousel rides and ice cream. The millionth ticketholder and family also will take a "victory lap" around the wooded lakeside on the replica of an 1863 Central Pacific engine that helped open the West.

Everyone else gets to enjoy an afternoon-long Showmobile program, including the Fairfax Symphony German Band, the Kings Park Community Band, storytelling puppetry by Jeanne Leckert and magic by Len Dileo.

At about 2:45 this Saturday, the train and carousel will take a break while park officials and dignitaries present awards to the Millionth Rider. Grove wasn't sure how many will speak (this being an election year), but you can always retire to the ice cream parlor for a sundae specially created to commemorate the day. -- Patricia Brennan. RIDING THE RAILS -- The C.P. Huntington minitrain runs from 11 to 8 Saturdays and Sundays and 11 to 6 weekdays to September 4. (From April 1 to mid-June and September 4 to October 30, it runs 10 to 2 weekdays and 11 to 8 weekends.) Both carousel and train rides are 50 cents each; free for tots under 2. Sundaes at the ice cream parlor start at $1.20.

GETTING THERE -- The park is at 7315 Ox Road, Fairfax Station. From the Beltway, take Braddock Road West (Exit 5), angle left onto Burke Lake Road and turn left at Ox Road. Park entry is free with a valid Fairfax County windshield sticker; non-county vehicles are assessed $4 each. Call 323-6601.