This is a very nice hike to a beautiful, secluded waterfall 1 hour from Nashville. It makes for the perfect day trip to the crisp and photogenic Machine Falls.
The Machine Falls loop at Short Springs Natural Area is a 1.6 mile round trip hike easily followed by white blazes. It is rated moderate difficulty due to the short, steep descent into a gorge where the falls is located. The trail is sparsely trafficked; there are usually quite a few people hanging out at the falls on the weekend. You can extend this part of the loop by continuing up to Adams Falls Trail.
There is also an alternate route to Bugsby Falls following Bobo Creek Trail, which is another loop trail that leads you down to Bobo Creek, where you can chose to do the 1.2 mile Laurel Bluff trail. This loops back to the Bobo Creek Trail. I highly recommend doing these trails as well if you have enough time. They aren't as heavily trafficked and are very pretty hikes.
Combining all loops: Machine Falls, Adams Falls, Laurel Bluff/Bobo Creek makes for an approximately 4-mile loop.