There’s about 12 miles or more of Philadelphia along the Delaware River, and actually a good deal more of it is the “River Wards” (Fishtown, Port Richmond, Bridesburg, Frankford etc) plus outright Northeast (Wissinoming, Tacony, Upper and Lower Torresdale etc) than Center and South Philly combined. Check any map.
There are also many neighborhoods abutting the Schuylkill River.
University City proper has been quite safe for several years, and has simply never been the most dangerous area of the city. It’s difficult to say that all of West Philly beyond UC is super-dangerous; some parts are better than ohers.
The levelling of buildings near Independence Mall happened in the 1950s, along with the demolition of the “Chinese Wall” and other Center City-area major renovations. But Old City (there is no “e”) real estate didn’t take off until the 1990s. This was classic artist-first, richer yuppies-next loft-driven, market-driven development/gentrification in old warehouse and factory stock. Nothing to do with tourism (although they will be happy to take your money…). Society Hill just south of that area was run down until the public-private partnership to renovate the area, which is the country’s largest collection of Colonial and Federal housing stock. That’s now the most expensive realestate in the city.
It’s difficult to say where the “bad areas” of the city are. Parts of North Philly (which is not the northernmost part of the city), Kensignton (variably defined), Nicetown and other parts of the NW, and parts of South (Southwest and the area down near, say, 8th and Wolf) and West Philly all have horrific areas just blocks from quite civilized areas. Poverty stricken and middle class or better residents often live just around the corner from each other. One block on either side of the el tracks is a drug and violence zone pretty much the whole length, yet Fishtown of all places is getting gentrified.
The only areas that seem to outright ghetto-free and extraordinarily safe for an urban environment are the Northeast proper, Manayunk, Roxborough and Center City itself.
It’s very difficult to make any generalizations about compass direction and poverty/crime here.