As an engineer, I'm fascinated by the intersection of tunnels and urban development. This city is a key link in the Underground Railroad's route from Chicago to the north. Interestingly, a group of city workers in June 1998 found storage bins under the sidewalk. The structures were built in the late 1850s, and physical evidence suggests that they were used to hide fugitive slaves. There was a tunnel that extended for five or six blocks that was a perfect place for a hiding place.