why is the shape of well is always round not square or triangle??

Question

shape from the inside of well, not the outside.

Answer 1

It is much easier to dig a round hole that deep into the earth, besides the side walls are a lot stronger, and resistant to caving in.

Answer 2

NOT ALL WELLS ARE ROUND INTERNALLY BUT THE MAJOR REASON IS BECAUSE IT'S EASIER TO DIG THAT WAY.