Lascaux Caves, France
The Lascaux Caves in France were discovered by four French teenagers in 1940. These caves offer some of the best examples of prehistoric cave art that are over 20,000 years old. But they were closed to the public in 1963 because visitors released humidity and carbon dioxide that damaged the cave art. Eventually, the French government spent $64 million to recreate the cave. But only scientists can view the original cave art.