Hey guys, I truthfully have not made this, I kid you not. There is no-one else who has been playing Minecraft in this family and I'm doubtful to whether this is a bug or Easter Egg. I thought at first it was maybe a dungeon, but there was no entrance, just water flowing out. This is no trick, no scheme, I was building on my town in my world and I wanted to explore a little, and I came across this. Also, when I opened my world, it was kinda laggy.
It was probably because of all the boats. I swear I didn't make this, and I wouldn't have the want to either. I took photos of it in-game so you guys can help me find out what this is.
Here's my Imgur album where I took all the photos. http://imgur.com/a/fOeSL