I want to build large cement steps in about a 3'x4' rectangle and about 4" tall.
Should I lay some rebar across when building them or will a piece of cement that big be fine to walk on without cracking?
always use re-bar - it would be best to pour a footing for it also.
i would add rebar it will help to support the weightof the concrete add steghten the structure of the step. as jimioc said it would also help to pour a footer to give added support to the corners.