Troytowns (trojaborgen) are mystic labyrinths that have existed around the world for thousands of years. Many Gotlandic labyrinths date back to the 19th century but this one is believed to be much older. According to the legend, a young girl built this labyrinth one stone a day when she was imprisoned in a cave nearby. The troytown impressed her prison guards so much that they let her free. 

Source: Region Gotland