CALIFORNIA: At 7.9 on the Richter scale, the 1906 earthquake in San Francisco and the resulting fires destroyed 80 percent of the city, including its imposing city hall, which was completed just 10 years before. Workers digging recently under the sidewalk on Hyde Street to plant a tree uncovered bricks and mortar from the structure. While remains of this building often turn up in the area, preservation specialists were surprised to find such large portions of its foundations still intact. —Samir S. Patel