Ellen DeGeneres is holding a live event in Philadelphia on Wednesday. But what it is exactly and why are currently a bit of a mystery.

The Ellen DeGeneres Show host announced via social media Monday night that she would "shut down a couple of blocks on Walnut St." here in Philadelphia on Wednesday. A Philadelphia city spokesperson has confirmed that the event will be concentrated on the 1600 block of Walnut St., with closures from Broad to 17th Streets (numbered streets between Broad and 17th  Street will remain open). Closure is scheduled to last from 1 p.m. to 8 p.m. The event itself will begin at 4 p.m., as per a Ellen DeGeneres Show representative.

DeGeneres herself, however, will not be visiting the city, as Greater Philadelphia Film Office executive director Sharon Pinkenson tells us.

"Ellen will not be in Philadelphia but she will be live from satellite engaging with her Philadelphia fans," Pinkenson says. However, correspondent Jeannie Klisiewicz will be on site at the event, a rep from the show confirmed.

Why DeGeneres' show is in town remains somewhat of a mystery. A source, however, tells us the show reached out to several University of Pennsylvania sororities inviting them to participate in the event, whatever it may be.

DeGeneres previously held a similarly secretive event in Philadelphia on Earth Day in 2010. In that instance, DeGeneres put on a contest that had fans following clues from the host doled out on social media. The hunt ended with giveaways for fans, according to a posting on the show's website.