Hike #48: 52 Hike Challenge: Flat Island Preserve, Leesburg. I arrived early at the 2,300-acre Flat Island Preserve in the Okahumpka Marsh and was the first one there and (briefly) had the whole island to myself. The trail system here is well maintained (and marked) by the Florida Trail Association. Don’t miss a chance to check out the scenic boardwalk. I will be back! Distance: 3.7 miles.