continuously operating commercial ski area (connected to Fonte Cerreto via cable car). History Hotel Campo Imperatore in Gran Sasso was Benito Mussolini's prison until his freeing on September 1943 by Nazi commandos in the Gran Sasso raid. The plateau is also the site of the Campo Imperatore station of the Rome Observatory, from which the Campo Imperatore Near-Earth Object Survey and other astronomical studies are carried out. At the southern edge of Campo Imperatore and within the bounds of the national park are three medieval hill towns once ruled by the Medicis; Calascio, which sits before the ancient fortress ruin of Rocca di Calascio, Santo Stefano di Sessanio, and Castel Del Monte. In 2005, a peak previously named "The Gendarme" was renamed "John Paul II Peak" on what would have been Pope John Paul II's 85th birthday. He had visited the Gran Sasso many times, saying it reminded him of the mountains of his native Poland. In January 2017, an avalanche hit Rigopiano hotel, killing 29. Science In 1984, a two-lane highway tunnel carrying the A24 motorway, the Traforo del Gran Sasso, was bored through the Gran Sasso Massif. In 1995, a second parallel tunnel was completed. Construction of the tunnel included an underground particle physics laboratory at Assergi, the Laboratori Nazionali del Gran Sasso or Gran Sasso National Laboratory. The first large experiments there started in 1989. The laboratory is composed of three large underground chambers, sometimes referred to collectively as the third tunnel, and lies beneath of rock. Construction of the laboratory and second tunnel faced opposition from Italian and international environmental groups including Pro-Natura International, LIPU and Club Alpino Italiano, as well as the World Wide Fund for Nature, Greenpeace, and Friends of the Earth. Environmentalists noted that the nuclear physics laboratory would lie on or near two major and highly active seismic faults, that construction of the tunnels would interfere with a major aquifer, and that construction waste would degrade an environmentally sensitive and significant area. Many credit the opposition created by the tunnel and laboratory construction with galvanizing the Italian environmental movement and leading to the creation of the Gran Sasso e Monti della Laga National Park in 1991. In recent years, the laboratory has itself begun promoting preservation of the Gran Sasso environment. Because of its low background radiation, the underground laboratory is used for experiments in particle and nuclear physics, including the study