Abstract. We review a cochain-free treatment of the classical van Kampen obstruction ϑ to embeddability of an n-polyhedron into R 2n and consider several analogues and generalizations of ϑ, including an extraordinary lift of ϑ which in the manifold case has been studied by J.-P. Dax. The following results are obtained.• The mod2 reduction of ϑ is incomplete, which answers a question of Sarkaria.• An odd-dimensional analogue of ϑ is a complete obstruction to linkless embeddability (="intrinsic unlinking") of the given n-polyhedron in R 2n+1 .• A "blown up" 1-parameter version of ϑ is a universal type 1 invariant of singular knots, i.e. knots in R 3 with a finite number of rigid transverse double points. We use it to decide in simple homological terms when a given integer-valued type 1 invariant of singular knots admits an integral arrow diagram (= Polyak-Viro) formula.• Settling a problem of Yashchenko in the metastable range, we obtain that every PL manifold N, non-embeddable in a given R m , m ≥, contains a subset X such that no map N → R m sends X and N \ X to disjoint sets.• We elaborate on McCrory's analysis of the Zeeman spectral sequence to geometrically characterize "k-co-connected and locally k-co-connected" polyhedra, which we embed in R 2n−k for k < n−3 2 extending the Penrose-Whitehead-Zeeman theorem.