What is northville tunnels?

Left to rot for 25 years. Anyone that grew up in with in 25 miles of Northville went here in the 80's and 90's. A gift from the leaders of 1920's Detroit. A place to let the county experiment on your kids from 1926 to 1974. Abandoned in 1974. Turned into a playground for delinquents. 3 miles of underground steam tunnels and 45 buildings to run around in.