Reykjadalur Hot Spring Thermal River is a popular hiking trail located in the Hveragerði area of Iceland. The trailhead is located at 64.0488421,-21.222614. The trail is about 3.5 km long and takes about 1.5 hours to complete. The trail leads to a hot spring river where visitors can enjoy a natural hot spring bath. The area is surrounded by lush green hills and offers stunning views of the surrounding landscape.