Llano de Maja (El Teide), Tenerife (2017). Francoist militias murdered more than 400 people on the island after 18 July 1936. An undefined number of ‘disappeared’ are believed to have been thrown into caves around the Llano de Maja within the Teide National Park.Valle de los Caídos III (Cuelgamuros), Madrid (2016). The Valley of the Fallen is the site of the largest mass grave in Spain. Built by the forced labour of political prisoners, and inaugurated on 1 April 1959, it contains the remains of 33.833 people.