Underground Railroad

What do you know about the Underground Railroad?

Jace - I think it is a railroad under the ground.
Madi - Old stuff underground
Kaden - the metal bars have to be really strong to hold all that dirt
Terren - I think underground is a railroad
Kelby - I think it is a train undergound going on a railroad track
Dani - I think it is a railroad track underground. It's the 2nd layer of a railroad track.
Gavin - A railroad track with rocks under it.
Kassie - An old bridge
Dylon - I think its a railroad track underground (3rd layer)
Sebastian - Under the water
Isaiah - I think that the underground railroad is a track that goes underground.