Charlotte and Pittsburgh are about 363 miles apart by road. Split the difference and you arrive near Richmond, the city closest to the halfway point between them. That splits the trip almost evenly — about 5 hr 12 min from Charlotte and 5 hr 6 min from Pittsburgh.
That's a half-day drive from each side, so Richmond suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If Richmond doesn't have what you're after, Raleigh and Washington are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Charlotte and Pittsburgh.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.