ok ok, how bout making a pond

hey, ok its me again, ok so i see that making an
aquarium might cost a lot
so how about making a pond, for an apartment
2 story apartment, meaning putting it outside, in
the cold. well it doesn't really get cold, but sometimes.
so how would i make a simple pond which will be good enough
for the koi. The width of the outside of the apartment might be 2-3
feet. Can you people help?
Thank you for your time