The Cuyahoga National Park is the quintessential urban park. Far from pristine, much of it has been reclaimed from industrial use. In fact, the canal was one of the major commercial corridors in the era before the interstate road, and even before the railroads. In spring, the park comes to life. And I don't just mean the people populating the hiking and biking trails.
Birds pass through from climes south.
The wildflowers come into bloom. You can't pass up seeing the Ohio state flower the buckeye in bloom. May. In honor of the tree, hit the Buckeye Trail, Ohio's epic loop, a branch of which travels through Cuyahoga. If you want to share a trail with crowds, hit the Cuyahoga Valley Towpath Trail. This is 30-plus miles, very gently graded, and wide enough to allow hordes of bikers and walkers.