For those who’d like to get their heart rate up while also running by historic sites to hilltop castles,the Castillo de Galeras & Castillo de la Atalaya trails are memorable. These are two separate routes. 

Subida Castillo de Galeras & Other Peninsula Sites

Just west of the port is a hilly peninsula overlooking the city of Cartagena and its harbor. One great running option is on the road up Monte Galeras to the Castillo. Access the Subida Castillo de Galeras from the Puenta Navantia, a small bridge across the canal in the Navantia shipyard area — not far from the port area (you can run there from the port, ~2 km, using the road along the canal). The trail is more of a road that is also used by cars (but fine for pedestrians), rising 130m over 2.8 km to the Castillo. Your climb is rewarded by great city & water views from this historic mountaintop site. 

Subida Castillo de Galeras. Google Street View

There’s also nice running on the eastern side of the peninsula. It’s 2.3 km from the Subida trailhead to the Navidad Lighthouse (faro), passing by the Playa del Espalmador (beach). You can also run to to the 12-century Bateria San Juan de la Podadera (at the southern tip of the peninsula. It’s 2.8 km from the Subida trailhead, passing by the Fajardo Castle, a fort, and a couple of scenic viewpoints. A full ‘loop’ of the eastern side can be ~8 km (very hilly!). 

Subida Castillo de la Atalaya

Castillo de la Atalaya (Castle of La Atalaya) is another hilltop climb to a castle. Subida al Castillo de La Atalaya is a steep concrete path climbing 180m over 1.5 km to the hilltop castle. There are great views the whole way, and a true reward from the top. The trail is accessed from Ctra. Atalaya on the western side of the canal in Barrio de la Concepción. 

Subida Castillo de la Atalaya. Google Street View