Spend 278 Days To Build A Dream Water Park

How long and where did I build?
I been working very hard with my 2 friends for 278days to completely build, This underground is in a very small private jungle in California (United State), We did together with three people (2 people is builder and one person is camera man)

How large is it?
Underground Dimension: Depth 5.2m , width 15.3m, height 8.3m, I knew the most of viewer they hard to believe but it real 100% by hand made with tools in video ! If you have any ideas, please leave a comment below my video.