Tim Waskow, age 9, of Sioux City, Iowa, for his question:

WHERE IS THE WORLD'S OLDEST BUILDING?

The world's oldest man made structure is a stack of lava blocks at Olduvai Gorge in what is now Tanzania. It was discovered in 1960 and is believed to date back to 1,750,000 B.C.

In 1965 scientists found evidence of buildings at Terra Amata near Nice, France. This location is said to date back to 300,000 B.C. In the excavation, it was found that one but had palisaded walls of 49 and 20 feet.

Oldest free standing structures in the world are thought to be the megalithic temples at Mgarr and Skarba in Malta and Ggantija in Gozo, an island near Malta. These structures date back to 3250 B.C.

Oldest castle in the world is at Gomdan, in the Yemen, which had 20 stories when it was built before 100 A. D.