There are many examples of groups that act on contractible simplicial complexes with a strict fundamental domain, e.g. free products with amalgamation, graph products of groups or more generally groups acting chamber transitively on buildings. I will discuss a construction that replaces the Davis complex by the so called Bestvina complex. This complex will have the smallest possible dimension equal to the virtual cohomological dimension of the group and will be equivariantly homotopy equivalent to the Davis complex. I will give examples of the Bestvina complex and discuss recent joint work with Tomasz Prytula where we consider the general setting of a strictly developable simple complex of groups and show that a Bredon cohomology of the fundamental group of the complex of groups can be computed from the relative cohomology groups of the strata. This has several useful applications.