Parque Natural del Estrecho (Estrecho Natural Park) is a fantastic spot for running at this southern end of the Iberian peninsula, adjacent to the town of Tarifa. This huge park is popular for windsurfing, miles of rugged beaches, and views of Morocco. Caution: open terrain, and long sections with few facilities.
The iconic run is the coastal path, which is for the most part a gentle trail run with good footing. There are a couple of options. The easiest option and a way to avoid some hills, is to start at the Observatorio del Estrecho. From there, go as long as you like, up to 7.7 km to the Torre de Guadalmesí. For the return, retrace your steps. The path is well way-marked. There are fantastic views the whole way. Starting from town: It’s 3.8 km to the observatory in the park. Take Paseo del Retiro for 2.4 km to the intersection, and then SHARP RIGHT on the road that leads to the obervatory.
Alternative Return/Additional Options in Park: For some variety, you could do an alternative return on the interior paths. It adds a couple of km and is much hillier (~500 foot gain), but it’s very scenic, with coastal views and fairly open terrain. For this option, take the Pista Colada del Camino de Alge at Restaurante Cañada del Patriarca. After a ~2.2 km steady climb, at an intersection, BEAR LEFT toward the Bateria de Costa “cascabel”, heading downhill, and continue on that path, past the Torreta Dep Buque España, to the start. You can also explore the numerous, scenic (and hilly) interior roads and paths.