There are some excellent beaches for running in the Tarragona area. The city’s principal beach, Playa El Miracle, isn’t very long. But there are some longer beaches east of Tarragona that are good for running. They are wide and fairly flat, featuring soft sand, but more reliably firm and runnable near the water. 

Platja Llarga (Llarga Beach). Located 5 km east of Tarragona. This 2.5 km long beach features soft sand. Can be firm near the water and runnable. Just east of the beach, the Camí de Ronda is a wooded, fairly narrow hiking trail that is good for trail running (moderate level).

Platja d’Altafulla. This beach has soft sand — even near the water. Not as reliably firm as Platja Llarga. 

Playa Torredembarra. 6 km long beach is similar to Platja d’Altafulla. Runnability is situational.  20 km east of Tarragona.