Library of Congress Tunnel
Bulfinch Tunnels. This is part of the tunnel system between the Adams and Jefferson buildings of the Library of Congress that is at least 4 levels deep. Charles Bullfinch gave a tour of Boston’s and Salem’s underground through their tunnels to President James Monroe and was hired to dig Washington D.C.’s tunnels.
Find out more in Salem Secret Underground:The History of the Tunnels in the City and its sequel Sub Rosa.