Translating to "in the heavens above," this group of six Eastern Orthodox monasteries were built on the sandstone pillars of central Greece that have endured a rocky past. As many as 20 monasteries were originally inhabited by monks in the 11th century. Only accessible by nets and ladders, the rock pillars served as protection against the Turkish invasion. After the invasion and bombings during World War II, there are only six remaining monasteries. Today, Meteora is an official UNESCO World Heritage site.