I was amazed, still am, at how much there is to explore in my own little state of Connecticut. Once we got our TT and started looking around, I found all sorts of things / places I didn't know about - museums, town parks, state parks, Corps of Engineer parks (had no idea Connecticut had those!), monuments, forts, walking and biking trails, etc. Every summer we plan at least one "new" place to explore in our own state, or explore more thoroughly where we've been before.
Start adding in neighboring states, and there is just so much to explore. People get so used to looking for something to do "over there", they never think to check out their own neighborhood.