Stroll through the hills of Punta Guaniquilla Nature Reserve and you could stumble across the Tunel Guaniquilla. This small but interesting rail tunnel dates back to the start of the 20th century, when Puerto Ricans relied on trains to get around the island.

Look upward before entering the tunnel to see the stone over the archway bearing an engraving saying 1908, marking the year it was built. This was one of the first tunnels built for Puerto Rico’s old rail network that previously crossed the island. For the first 50 years of the 20th century, trains were a popular method of travel here, but they fell into disuse and left behind landmarks such as this hidden hillside tunnel.

The entrance to the tunnel blends into the landscape. Look for the stone archway that is buried in the hillside, with undergrowth rising around its edges and hanging over the tunnel. The stones beneath your feet are the remnants of ballast that would once have been the track bed, the only reminder of its past as a railway.

Walk through the short tunnel and picture steam trains running through it to serve the local communities. The tunnel is only 100 feet (30 meters) long and it has stayed wholly intact, although the rails have long since disappeared. A hollow in the middle of the tunnel was used as a place of safety for people avoiding trains when walking through the tunnel.

Follow the old railroad tunnel path through Punta Guaniquilla Nature Reserve. Trails in the reserve lead to a stunning lagoon with moon-like rock formations, as well as beautiful windswept beaches.

In order to visit the Tunel Guaniquilla you need to notify the Fideicomiso, the Conservation Trust of Puerto Rico. Speak to them and they can give you tips on finding the tunnel and walking through the nature reserve. The tunnel is over 4 miles (7 kilometers) from Cabo Rojo and can only be reached on foot. Explore the tunnel and surrounding area for free.