County Preserve
Goat Island Preserve Shows the Rural Side of the Trinity
Goat Island Preserve spreads across 637 acres of unincorporated land in the southeastern corner of the county, out past Hutchins, Wilmer, and Seagoville. It rides the Trinity River Greenbelt and butts right up against the river, which gives the south county a feel nothing like the paved trail loops downtown.
There are nine miles of soft-surface trail here, kept up by the Dallas Off-Road Bicycle Association, plus four ponds and stretches of bottomland woods along the water. The way in is at 2800 Post Oak Road, where it meets Fulghum Road, and the gates run sunrise to sunset.
This is river-bottom land, so the trails shift with the Trinity, and high water can rework them. After a wet spell, it's worth a quick check on conditions before you haul the bike out there.
Source to confirm: Dallas County - Goat Island Preserve