Touch a Wall Street building scarred by a 1920 terrorist bombing.

On September 16, 1920, a horse-drawn carriage carrying a large bomb was driven to the intersection of Wall Street and Broad Street. When detonated, the bomb sent fragments hurtling into the surrounding buildings, killing 39 people.

The explosion left craters ranging in size from small, missing chunks of limestone to deeper baseball-sized pits on the walls of 23 Wall Street, today the only remaining reminders of a long forgotten terrorist attack.

Although it's believed that Italian anarchists carried out the attack, the case was never resolved. Until September 11, 2001, the Wall Street bombing was the deadliest terrorist attack in the history of New York City.