Labyrinth of Tunnels?

This photo shows North End buildings that are adjacent to the Copp's Hill Burying Ground. The harbor is in the distance. Written on the back of this photo are the words, "Do you know the whole North End once had a set of tunnels that kept certain people in touch with each other’s houses, and the burying-ground, and the sea?"

Thurber collected several photographs of Copp's Hill Burying Ground, which, according to his notes, was very close to the location of Pickman's North End studio. 

Thurber's notes include descriptions of several of Pickman's paintings that have never been found or seen by anyone else. One painting describes "a dance on Copp’s Hill among the tombs with the background of today." 

The Mather Tomb in Copp's Hill Burying Ground, final resting place of Cotton Mather. According to Thurber's notes, Pickman claimed that Mather witnessed the hanging of Pickman's four-times-great-grandmother in Salem, Massachusetts.