  This is a revised version of the author's PhD thesis, including the
corrections by the examiners. It also includes a few additional small
corrections.
  In this thesis the objects of study are classifying spaces of groups with
stabilisers in a given family of subgroups. Given a group G and a family of
subgroups we study the minimal dimension a classifying space can have. We focus
on classifying spaces with virtually cyclic stabilisers.
