When famed archeologist Mary Leakey travels, she likes to have a purpose. "I very seldom go just to do nothing," she says. "I like to go with some objective." She has flown from her home outside Nairobi in Kenya to lecture Friday at the Smithsonian (8 p.m., Baird Auditorium) and to promote her new autobiography, "Disclosing the Past."

Born in 1913 in London, she and her husband, archeologist Louis Leakey, formed a 30-year partnership in their search for and study of prehistoric human fossils at Olduvai Gorge and elsewhere in East Africa. Their son Richard is also a noted archeologist.

She does, occasionally, go on a vacation, and among her favorite destinations are:

*Southwest France: "It's top priority. I was there as a child. It's beautiful country, and there are a lot of prehistoric remains. I like to drive slowly through that country and stop at small villages."

*Baja California: "The desert part, because there are no people and it's quite untamed. I stayed with friends who had a ranch. We did look at rock paintings, but it was just a holiday."

*Serengeti Plain, Tanzania: A grasslands and wildlife refuge. "Serengeti has always been a favorite of mine. That's where Olduvai Gorge is." Before moving to Nairobi a year ago, her home was at Olduvai.