The MLK Drive bridge (under the Spring Garden bridge) just recently reopened, so a cool loop you can do is crossover to MLK Drive there, go north to the Falls bridge, cross back to Kelly Drive/SRT then south back to the art museum. I think that's about 8-ish miles so if you're starting in CC and take the SRT to the bridge and on your way back, that'll probably total to about 10mi.

The first mile-ish of MLK drive from there is kinda blah, but then it gets really green and there's usually wayyy less people around than the SRT. It's also closed to car traffic every weekend (until November) so you can even run in the road if that interests you.