Making Minecraft Spherical

I was recently thinking about this... We've been building houses and other structures using plum lines and water levels all the time before afordable optics came in play. This kinda means most of our buildings are actualy polar rather than cartesian. Surely enough given the size of earth the error is quite tiny. But it's funny thinking about how the room i am sitting in right now is shaped like frustum with spherical floor and ceiling, rather than block. Despite what architecture drawing says...