Especially since the addition of the Sitton Gulch trail and entrance point at the bottom of the canyon, this area is a favorite of ours. The Sitton Gulch route allows access to the lower falls without a lot of stair climbing, but with a lot of nice creekside hiking. Of course coming down from the top and returning is much more challenging, but still well worth it with views of both falls. And the Wet Rim Loop has always provided great views. These are good hikes at any season, but spring has a lot of water flow over the falls and winter has a lot of ice and frost on the canyon walls around the falls. And now the Bear Creek trail has been renewed as well. http://gastateparks.org/net/go/parks.aspx?locid=38&show=map
Lookout Mtn Five Points
Five Points is another mountain bike venue with trails that criss-cross rolling hills and flat sections. Another place where a map is very much a necessity, though.
Lookout Mtn Lula Lake
Open only two days a month, this still provides a wonderful loop hike with views of Chattanooga Valley from the bluff, the falls from above or below, and Lula Lake. A good choice for an easy to moderate hiking day. http://lulalake.org/project/lula-lake-core-property/