This Puerto Rican original railroad tunnel is often called El Tunel de Guajataca. It is located on the western edge of the well known Guajataca Beach area of Isabela. El Tunel Negro (The Black Tunnel), is another railroad tunnel nearby but on the higher elevations of Quebradillas on the east side of the Guajataca River and its curved bearing permits for very little light to pass through. A leisurely stroll thru the Guajataca Tunnel leads to another spectacular beach. (A third railroad tunnel can be found in Cabo Rojo.)

The Guajataca Tunnel was constructed in the first years of the 20th century, as the American Railroad Company of Puerto Rico made a rapid push to expand transportation infrastructure. Puerto Rico had been annexed to the United States under the Treaty of Paris in 1898, and the Americans were eager for quick delivery of cheap sugar. However, in order for (tariff-free) exports to move at the desired pace, there would need to be a significant expansion of the national railway system.

The Guajataca Tunnel was part of a larger construction project that would eventually connect San Juan in the north to Ponce in the south. At around 514 feet long the Black Tunnel is the longer of the two tunnels connected by a tall steel bridge known as the Red Bridge spanning the Guajataca River. Trains carrying both passengers and sugarcane rumbled over and through them until 1953.

Although now only a paved walking path runs through El Tunel de Guajataca, it remains significant as both a feat of engineering and a marker of a moment of political transition. It was declared a historical monument in 2000.