Alexandrov spaces are metric generalizations of Riemannian manifolds with sectional curvature bounds. The boundary of an Alexandrov space M may decompose into several boundary strata. If M has positive curvature, it is quite well understood how the number of boundary strata determines the homeomorphism type of M as a stratified space. This book deals with the case that M has nonnegative curvature. The author Andreas Worner begins with an introduction to Alexandrov geometry, which requires only some familiarity with Riemannian geometry. Then boundary strata are investigated more closely. After...