I have a house in Queens, NY that was part of the Underground Railroad.
From the outside it is a 3 story building.
But inside between the 2nd and 3rd floor there is an actual hidden staircase in the wall on the 2nd and on the floor of the 3rd that goes to a hidden floor in between the 2 where refugee slave were hidden.
Not every house with a hidden cook lab was part of the railroad however 😛