It seems "The Hills" stars are all running to a flatter playground these days.

On Saturday (April 24), Kristin Cavallari became the third "Hills" in the past month to host a Las Vegas party. A bikini-clad Cavallari hosted a pool party at Liquid Pool Lounge.

Earlier in the month, Audrina Patridge hosted a shindig at the Wet Republic Pool at the MGM Grand, and Heidi Montag brought her surgically enhanced bod to the actual opening of the Liquid Pool Lounge.

Apparently "Hills" hellion Spencer Pratt isn't getting any invites to host parties these days. According to Cavallari, the guy we love to hate won't be returning to the show to stir up trouble.