We prove that a globally hyperbolic spacetime with its causality relation is a bicontinuous poset whose interval topology is the manifold topology. This implies that from only a countable

dense set of events and the causality relation, it

is possible to reconstruct a globally hyperbolic

spacetime in a purely order theoretic manner. The

ultimate reason for this is that globally hyperbolic spacetimes belong to a category that is equivalent to a special category of domains called interval domains.

We obtain a mathematical setting in which one

can study causality independently of geometry

and differentiable structure, and which also

suggests that spacetime emanates from

something discrete.