Boulder Spring is a 5th magnitude spring. The spring head is a small pool in an area of limerock outcrop, with large limestone boulders in the spring pool and run. Water flows from vents at the base of the hillside and in sand boils in the spring run as it flows about 0.3 mile toward the northwest to Sulphur Run.
Boulder Spring is located in the Seminole State Forest about 1.6 miles southeast of Cassia. From the south entrance of Seminole State Forest on State Road 46 (about 0.4 mile west of the Wekiva River), turn north and drive past the stop sign, through the gate, and cross the bridge over Black Water Creek. Drive about 0.2 mile past the bridge to the next intersection. Turn right at the intersection and go 1.2 miles to the intersection of two horse trails and Palatka Road. Walk toward the left onto the northernmost horse trail (vehicles are not permitted on the horse trails) and go 0.5 to 0.6 mile to the clearing on right side of trail. Walk about 200 feet toward the northeast to Boulder Springs. Access and fee information can be obtained at the Seminole State Forest south entrance.