In 1991, construction workers here uncovered more than 400 stacked wooden caskets, just 16ft to 28ft below street level. The boxes contained the remains of both enslaved and free African Americans from the 17th and 18th centuries (from 1697, nearby Trinity Church refused them burial in its graveyard). Today, a poignant memorial site and a visitor center with four rooms of educational displays honor the estimated 15,000 men, women and children buried in America's largest and oldest African cemetery.

　　As the visitor center is located inside a federal building (also home to the Internal Revenue Service), you'll need to go through airport-like security screening.