Don Phillips, age 12, of Monroe, La., for his question:

WHEN WAS THE PANTHEON BUILT?

The Pantheon is an architectural masterpiece of ancient Rome. Construction was completed in 126 A.D. during the reign of Emperor Hadrian, who may have helped design it. The building was used as a church by Christians between the early 600s and 1885.

The Pantheon is a circular building topped by a dome. A rectangular porch stretches 100 feet across the front. Over the porch is a triangular roof supported by 16 Corinthian columns of granite, each 42 feet high.

The entrance to the temple still has its original bronze doors.

The Pantheon was the first Roman building to emphasize interior space, rather than exterior form. The inside of the temple is a circular chamber 144 feet in diameter. The dome, supported by eight large piers, is 144 feet above the floor at its apex, or highest point.

The only natural light comes in through an opening 30 feet in diameter at the apex. Colored marble designs decorate the floor and walls.