Bethlehem (15 minutes west) is the obvious add-on — for the SteelStacks music and arts complex on the rusted hulks of the old Bethlehem Steel mill, and for the Moravian Bookshop in the historic district. Allentown further west has the Da Vinci Science Center and Dorney Park.
For a more rural day, head north into the Delaware Water Gap National Recreation Area — 30 minutes up I-80 — with kayaking, hiking the Mt Tammany trail, and the Bushkill Falls. South towards Bucks County puts you in the riverine villages of New Hope and Lambertville. Philadelphia is about 90 minutes south on the turnpike for a full day in the city.
