At over 175 meters long, the world's largest submarine is almost twice the length of a standard rugby union pitch, but what's it like to be inside, and how does it work?

The Dmitriy Donskoy is far narrower than it is long, at 25 meters, but don't be fooled by its streamlined design. This submarine can displace 48,000 tonnes of water - that's over 19 Olympic-sized swimming pools filled to the brim.

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