  Let $K$ be a field and let $A$ be a subring of $K$. We consider properties
and applications of a compact, Hausdorff topology called the "ultrafilter
topology" defined on the space Zar$(K|A)$ of all valuation domains having $K$
as quotient field and containing $A$. We show that the ultrafilter topology
coincides with the constructible topology on the abstract Riemann-Zariski
surface Zar$(K|A)$. We extend results regarding distinguished spectral
topologies on spaces of valuation domains.
