Selena Gomez look beyond sexy, almost without trying, as she rocked out at the Mann Center in Philadelphia, while Justin Bieber dropped in for some PDA in the city where their relationship, or at least the rumors about it, began.

Justin flew in and joined Selena, who was also promoting her Dream Out Loud apparel collection at KMart.

Last December, the two were spotted clinging to each other while dining out in the city of brotherly love.

Gossip Web site TMZ tracked down the pair at an International House of Pancakes on Wednesday (Dec. 8). It was the first time they appeared to be more than friends.

She was back in Philadelphia Aug. 19 to perform at the Mann Center for the Performing Arts as part of her tour.

“I am so excited to see my incredible fans on tour. We’re working a great production, and set lists including some surprise covers. I want to make sure everyone has a fun time,” she said in a statement.

Selena will be heading back to Los Angeles next weekend to host live from the black carpet at the MTV Video Music Awards.

Check out Selena’s photos; click to enlarge.

“Woohoo! MTV VMAs on Aug 28. I am so excited to be hosting the preshow!!!” the 19-year-old Tweeted.

Justin will also be on hand at the VMA’s and he’s expected to be one of the guests at Kim Kardashian’s Santa Barbara wedding.

It will be interesting to see if Selena attends with him.

At the Mann Center concert, Allstar Weekend opened Selena Gomez & The Scene.

The star of the Disney Channel’s “Wizards of Waverly Place,” which is in its last season, released her third album on June 28, and is starring in Fox’s feature film “Monte Carlo.”

Her new single, “Who Says,” debuted on the Top 10 on the charts and was the most added single at Top 40 radio overtaking new singles by Bruno Mars and Britney Spears.

“Who Says” will be featured on Selena Gomez & The Scene’s third upcoming summer album.

Check out her performance below, and her photos from the show.