  Classical correlations without predefined causal order arise from processes
where parties manipulate random variables, and where the order of these
interactions is not predefined. No assumption on the causal order of the
parties is made, but the processes are restricted to be logically consistent
under any choice of the parties' operations. It is known that for three parties
or more, this set of processes is larger than the set of processes achievable
in a predefined ordering of the parties. Here, we model all classical processes
without predefined causal order geometrically and find that the set of such
processes forms a polytope. Additionally, we model a smaller polytope --- the
deterministic-extrema polytope --- where all extremal points represent
deterministic processes. This polytope excludes probabilistic processes that
must be --- quite unnaturally --- fine-tuned, because any variation of the
weights in a decomposition into deterministic processes leads to a logical
inconsistency.
