Donald Glass, age 12, of Winston Salem, N.C., for his question:

IS THERE A CITY ON TOP OF A CITY IN ATLANTA, GA?

In downtown Atlanta, Ga., there's a section called Underground Atlanta that is actually a city on top of a city. In the late 1800s, trains came into the central area of town causing great congestion, so a viaduct was built over the main streets. The trains soon went elsewhere, and the network of underground streets stood empty for more than half a century.

Two Georgia Tech graduates opened the underground area in 1968 as a spectacular tourist attraction. More than 40 shops and restaurants stretch more than two and a half square blocks