It's Florida: It's Flat
The Jacksonville-Baldwin Rail Trail is just west of the I-295 loop and just north of I-10. The east trailhead is on Imeson Rd.
The trail is mostly used by bike riders, but horses and pedestrians are also allowed.
It crosses many roads, and passes by many semi-rural residential areas. (Many large properties with ponds, barns, work sheds, etc.)
Unlike some rail trails, which are hard pack sand / dirt / gravel, this one is paved.
Because of Florida's abundant trees & vegetation, shade is plentiful.
One highlight is Camp Milton, which was a confederate camp during the Civil War. Exploring Camp Milton adds about two miles to your day. (I'm not sure, but I believe it is pedestrians only.) Part of Camp Milton's trails are paved, but there is a lo-o-ong boardwalk around the old earthworks. Camp Milton is just about halfway west on the rail trail.
The trailhead just across Halsema Rd. from Camp Milton has tire pumps and other gear to help bikers.
The other highlight is the Baldwin Station, a historical train stop converted to a town park.
Benches & trash cans are regularly located along the trail, which has very little garbage despite being so close to civilization.
The trailheads at both ends have restrooms, plus there is one at Camp Milton just off the rail trail, at Baldwin Station, and a portapotty at the Halsema Rd. trailhead.
Snakes & gators are always a possibility, as much of the non-developed terrain is low & swampy, or simply soaking wet from Florida's daily afternoon rainstorm.
The Jacksonville-Baldwin Rail Trail ends just west of the town of Baldwin, on Brandy Branch Rd.
Check out the Triplog.