  Geometric frustration describes the inability of a local molecular
arrangement, such as icosahedra found in metallic glasses and in model atomic
glass-formers, to tile space. Local icosahedral order however is strongly
frustrated in Euclidean space, which obscures any causal relationship with the
observed dynamical slowdown. Here we relieve frustration in a model
glass-forming liquid by curving 3-dimensional space onto the surface of a
4-dimensional hypersphere. For sufficient curvature, frustration vanishes and
the liquid freezes in a fully icosahedral structure via a sharp `transition'.
Frustration increases upon reducing the curvature, and the transition to the
icosahedral state smoothens while glassy dynamics emerges. Decreasing the
curvature leads to decoupling between dynamical and structural length scales
and the decrease of kinetic fragility. This sheds light on the observed
glass-forming behavior in the Euclidean space.
