ALTON, Ill. (KTVI) – A mysterious 19-century tunnel has been found underground on an Illinois resident’s property.

“A lot of brick,” said Gary Machens, who discovered the tunnel. “Whatever they built this for, it took a lot of men and a lot of hours. You know, one guy didn’t do this.”

Machens first found the tunnel when he noticed his sidewalk starting to slope.

“Had a problem here at the sidewalk and as we were doing some excavating and repacking of the rock here, we discovered this tunnel here,” he said. “According to historians here in the Alton area, this tunnel was put in here around 1840.”

When the West Alton farmer and his wife first moved into their home, he already knew of its history, which dates back to the 1890s.

Machens believes the change in elevation from 1895, when the brick-lined street was put down, covered the opening to the underground mystery.

“Why is it stair-stepped like this?” Machens said. “Why is that in there? Do you see the offset in the brick? And if you look along this wall, it turns that way a little bit. Look down along this wall.”

Whether for ice storage, a carriage or part of the Underground Railroad, it’s anyone’s guess.

“It’s unique. There are a few tunnels around the Alton area, we found out since we checked with the Landmark Historic Society,” Machen said. “It’s probably been used for maybe a half-dozen things through the years, anywhere from an icehouse to a root cellar and maybe a few other options.”

He said he’s got maps that go back to 1863, when no house was on the property.

“It could have been used for part of the Underground Railroad,” he continued. “There’s no proof of that, but there was a major ferry here in the Alton area to the Missouri side, and it’s possible it could have been used for that.”

Machens is open to the idea of opening the tunnel for tours if he can get the city or someone to help with logistics and cost.

For now, he has to fix his sidewalk and seal up the tunnel.

“So, it was at least 9 feet tall,” he said. “We’re standing on about a foot of dirt and it’s 9 feet wide and how far back it goes, we don’t know. We know it goes back 60 feet.”

Machens, a history lover, says he wants to preserve the mysterious tunnel.

“Yes, three former mayors of Alton have lived in this house through the years,” Machens said. “I don’t know if any of them knew about this. The house was built in 1890, the tunnel is believed from 1840, so it was here for 50 years. What it was used for, I don’t know.”