Most guarded places on Earth: What are these 25 places hiding?

This world has many secrets, and those secrets are hidden from the public’s eye in protected locations scattered around the globe.

But what makes those guarded items so special? What could possibly be in these nuclear bomb-proof vaults, military zones and restricted buildings to warrant such extreme security measures?

It turns out people want to hide more than just gold, jewels and priceless manuscripts.

Secret military operations, freedom, royal correspondence, dangerous people — depending on the country, a variety of materials are considered so important that they must be kept safe at all costs. Often, the guarded items are so precious that not even the guards are allowed to check on them.

Some of these locations aren’t even protecting invaluable items — just a lot full of cars — but they’re still incredibly secured. But, deep in granite caves, across the frozen tundra in Arctic countries only accessible by plane, or protected by hundreds of specially-trained guards, countries have thought up truly ingenious ways of safeguarding their most valuable possessions.

From tiny seeds to gold bullion, the world's most precious treasures are hiding in safes that not even Jeff Sitar could crack.

Here are 25 of the most heavily guarded places on Earth — and what they’re guarding.