welcome to sealand. >> reporter: it wasn't always named sealand, and it was never intended to be a countryy's roughs tower, it was a hastily constructed nautical fort, one of several the british set up in the north sea during world war ii. equipped with anti-aircraft artillery, these forts were designed to prevent german bombing raids on london. during the war, more than 100 royal marines were crammed into these towers for months on end. descending the seven-story towers, it feels and smells like a cross between a tree house and a diesel-soaked submarine. first up, the first class bedroom suite. >> it's a nice one. >> nice tv. >> reporter: our claustrophobic tour continued downward. >> now we're underwater at this point. >> yeah. >> so we've still got a couple floors to go. >> you hear ships going past. you hear the propellers going ding, ding, ding, ding. >> reporter: like many countries, there's a national cathedral. >> you have freedom of worship in sealand. i think there's even a koran here somewhere. >> reporter: on the bottom floor, the jail. >> two days in the brig. bread and water.