Wow- how crowded can you get? A good friend and brother of my went to Japan for four years as a missionary and he told me real estate is so scarce that the Japenese are stacking overseas shipping container and turning them inot apartments- wow again!
I saw a history channel show not too long ago about how the Japanese are designing a new self-sustaining sky city, or something like that! It's been a while, I don't remember exactly, but it was something like 2 or 3 miles high and every "floor" was circular with apartment-offices, farmer's markets type, etc. Each floor, if I remember correctly, would it's own mini-city. It was amazing, but the city planners in Japan were saying that this building would not be just something new and different, but a strict necessity at one point because of Japan's over-population.
The first and I believe still the biggest is in Texas and was built nearly ten years ago .
There are two water parks in Myrtle beach that have them. and two in Ohio that I know of. There are probably a lot more.
One in Myrtle Beach is as big or bigger than the one shown in the vidio
You won't find them as full as that one (because liability/ saftey here in the states)
But yes they are a lot of fun