To celebrate the grand opening of five new downtown retailers at CitiPark, River City Company will host a block party on Sept. 21 at 4 p.m. The new stores are part of Project: PopUp, the Chattanooga retail incubator meant to attract and support new opportunities in downtown’s City Center district. Retailers include Go Bagel, Iron Labs, Sewn to the Sky, O.C. Buckels & Co. and Tasty Daylight Donuts. For more information, visit www.facebook.com/ProjectPopUp.