Two men dug a secret 30-foot tunnel in Toronto as a “man cave,” police said Monday.

The tunnel discovered last week near a university campus led to an investigation by police that found the pair, both in their twenties, had built it with no criminal intent.

“It is simply two guys who just wanted to dig a cave,” said Toronto police spokesman Victor Kwong, according to CBC News. “They just wanted to dig a cave to hang out.”

No charges have been filed and the investigation is considered complete, police said. The police said the two unnamed men didn’t have formal engineering training, making the scale of the tunnel an impressive feat. It measures about 30 feet long, six feet tall and three feet wide.

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Write to Justin Worland at justin.worland@time.com.