In November, the crew at Lennar's Central Park West high-rise development in Irvine, Calif., uncovered the remains of a 30,000-year-old giant ground sloth. The animal would have been 6 feet tall and weighed 3,500 pounds when it roamed the earth during the Ice Age. The excavated area within the 42-acre jobsite was cordoned off so that the fossilized bones could be removed carefully and brought to a warehouse to be cleaned, tagged, and stored.

Building homes requires digging up land, and builders unearth all kinds of things, including human skeletons. “We survey all of our sites, looking for graveyards,” says Charlie Bostwick, president of the South region for Atlanta-based John Wieland Homes and Neighborhoods. When they're found, the builder often separates that area with fencing or landscaping.

In December, Wieland installed a room inside the clubhouse for its Legacy at the River Line community in Mableton, Ga., that, says Bostwick, displays Civil War–era bullets and shells found on the site. Legacy is located on the southern extension of Johnston's River Line, a seven-mile-long system of fortifications built in the summer of 1864 to channel attacking Union armies into an open field. Maps of the fortifications are found in the clubhouse, too.

Learn more about markets featured in this article: Atlanta, GA, Los Angeles, CA.