Characterize triangulable topological spaces
Characterize the class of topological spaces that admit a triangulation (i.e., are homeomorphic to a polyhedron arising from a finite simplicial complex), and ascertain triangulability criteria for non-differentiable manifolds in dimensions greater than three.
References
All differentiable manifolds have triangulations, but a complete characterization of the class of topological spaces that have a triangulation is not known. Every topological 2 or 3-manifold has a triangulation, but there is a (non-smooth) 4-manifold that cannot have a triangulation (it is related to the Lie group E_8 ). The situation for non-differentiable manifolds in higher dimensions remains uncertain.
— Algebraic Topology
(1304.7846 - Robins, 2013) in Subsection "Simplicial complexes" within Section "Homology"