The same crystalline waters swooshing the pebbled coast of San Lucas Island were once murked by the crimson red of blood. From 1873 to 1991, the island served as Costa Rica’s principal penitentiary, where some of the country’s worst criminals were sent to serve often short and torturous sentences. Due to its offshore location, the prison is regularly referred to as Costa Rica’s Alcatraz.

Despite a still-recent history, the island looks much different today than it did at the apex of its haunting days. Turned into a national park and painstakingly cared for and maintained, the entrance to San Lucas features a quaint white bridge with cobalt blue poles, whose walkway leads straight into a tourist sign with the first of many poignant messages: “Ocean and forest protecting history.”

Yet, a few steps in and the reality of its past begins to hit. The first stop of a walking tour leads to a makeshift hospital. The doors of the small white and grey wooden house stay tightly shut until a guide makes sure everyone is ready to enter; otherwise, its rooms quickly fill up with bats and insects. The beautifully tiled floors contrast with pictures of the convalescing prisoners who once laid crammed in the house awaiting the prison’s only doctor, a veterinarian sent to the island after many desperate pleas for medical support.