This movie was from about 10 years or so ago.  Seems like it was on Sci-Fi or Chiller.  It was about some young friends driving.  They got off the highway and went to this rest stop/park.  There was a restroom at the top of a hill.  There were stairs leading up the hill.  There were weird people around here and there.  One of the friends comes up missing.  Then another.  At one point there is a flea market at the bottom of the hill where these weird people are selling items. Then all but one, I think, of the friends has disappeared and the last one figures out that they are disappearing through a stall in the restroom and the weird people are going through the stall/stalls through the wall and living under the restroom and they kidnap people and make them work under there.  I can’t really remember for sure.  Thanks!