Investigators said the tunnel led to two small caves, one that appeared to be a bedroom and another with a ceiling over 5 feet high.
Yosue Joel Rios, 25, approached officers while they were investigating the tunnel and told them it was his home.
Rios, who was wanted in Arlington County for failure to appear on a traffic violation, was arrested on a destruction of property charge.
"To the left was a small alcove that was a little smaller where we thought he was sleeping. The room to the right was a bit larger from floor to ceiling that was about 5-1/2 feet tall, so you could almost stand up," Sgt. Natalie Hinesley told CNN.
She said the Fairfax Department of Public Works filled in the tunnel and caves Monday morning.
"I've never seen an underground cave, but I have seen homeless camps like tents and makeshift shelters above ground. But I have never seen something as intricate as this," Hinesley said.
