Here is pi to 1,000,000 places. Utterly pointless, but there you go.
And the reason something as "simple" as a circle has it is because it has an infinite number of side. Every single minute straight line you add to give the
appearance of a circle can always have another drawn halfway between.
It's like trying to count the frames of animation when you move your finger. There's always another halfway, because in real life you can't just skip space, you must pass through it