One of Lower Manhattan’s most fascinating, and controversial, stories of recent years circulates around the new African Burial Ground National Monument site. It began when a construction project in 1991 uncovered a burial ground of slaves – more than 400 caskets were found – from an age when New York had more slaves than any American city outside Charleston, South Carolina. Outside you can see part of the site now enveloped by buildings, and the compact visitors center does a masterful job at retelling African-American history in the city. 290 Broadway between Duane & Elk Sts, Lower Manhattan…