2. Lascaux Caves, France
The Lascaux caves in southwestern France provide stunning examples of prehistoric cave paintings. The caves hold a series of prehistoric paintings and engravings thought to be about 20,000 years old. The paintings depict bison, ibex, stags, and cattle, among other things, and plaster the walls everywhere you look. The most amazing example is found in the Hall of the Bulls, known for four bull murals. One of them is 17 feet long.
Unfortunately, the presence of people has been destructive to the irreplaceable works of art. And not only that, but the caves have been plagued by fungi and black mold. Therefore, the caves themselves have been off-limits to humans since the 1960s. Luckily, a museum and cave replica recently opened right next to the caves, so you can at least brush by the experience.