Can't wait 'til First Friday to get your art fix in downtown Lancaster? You don't have to. You can sate your appetite this weekend, too, during the Rivertowns Fourth Friday celebration. Each month, the towns of Columbia, Marietta and Wrightsville showcase their creative offerings in much the same way downtown Lancaster does. Friday from 5 to 9 p.m., visitors can enjoy a variety of art exhibits and explore specialty and antiques shops in all three towns.