Like many mountain bike trails in this area of Florida, Loyce E. Harpe Park (formerly Carter Rd Park) is a former phosphate mining operation. The trail meanders through the woods around man-made ponds (borrow pits). The main trail is relatively flat and only has the occasional root to throw at you.
For the more serious rider, there are several fingers off of the main trail that clamber over piles of rock and dirt left from the former mining operation. These fingers are much more challenging, and the local MTB club is adding berms and other obstacles.
Some of the downsides, as of this writing, are poor signage in areas, making it easy for neophyte riders to suddenly find themselves in an area they may not be ready for. This is also a one-way trail, something not obvious from the (otherwise quite good) trail maps and other materials on site.