#7 Lascaux Caves, France
The complex series of caves which are even listed as an UNESCO World Heritage Site, is home to one of the most famous examples of Palaeolithic cave paintings. After 2008 the caves were completely closed off to the public due to a fungal breakout and only a handful of scientists are allowed to enter the caves.
#6 Svalbard Global Seed Vault, Norway
The Svalbard Global Seed Vault is a seed bank that stores all variety of seeds from all over the world. The idea behind this is to provide with a safety cabinet against a major accidental loss of diversity.
#5 Coca-Cola Recipe Vault
The Coca-Cola recipe is one of the most heavily guarded secret. Only a handful of people know the formula and to protect this recipe the company has a high-tech vault storing the secret formula.