We investigate the influence of space curvature, and of the associated "frustration", on the dynamics of a model glassformer: a monatomic liquid on the hyperbolic plane. We find that the system's fragility, i.e. the sensitivity of the relaxation time to temperature changes, increases as one decreases the frustration. As a result, curving space provides a way to tune fragility and make it as large as wanted. We also show that the nature of the emerging "dynamic heterogeneities", another distinctive feature of slowly relaxing systems, is directly connected to the presence of frustration-induced topological defects.Among the many anomalous properties associated with glass formation, "fragility" is one that has attracted much attention [1,2,3,4,5,6,7]. Large fragility, i.e. large deviation of the temperature dependence of the viscosity and of the structural relaxation time from an Arrhenius behavior, is usually taken as the signature of a collective phenomenon that grows as temperature decreases. This is certainly one incentive for the continuing search for a theory of the glass transition [2,4,5,6,7]. Yet, the absence of a simple glassforming liquid model in which one can control the degree of fragility, hence the extent to which collective behavior develops, has hindered progress on developing and testing candidate theories.Since the early work of Frank[8], a promising line of research on supercooled liquids and the glass transition has relied on the concept of "geometric frustration" [7,9,10]. Frustration in this context can be defined as an incompatibility between extension of the local order preferred in a liquid and tiling of the whole space. The paradigm is the icosahedral order in metallic liquids and glasses, which although locally favored cannot tile space due to topological reasons [8]. Frustration of the icosahedral order, however, can be suppressed by leaving the Euclidean world and curving space [9,10]. In a series of insightful articles [10,11,12], Nelson and collaborators have proposed a simpler two-dimensional (2D) analog: by placing a liquid of disks on a 2D manifold of constant negative curvature (the hyperbolic plane), the local hexagonal order that can tile the ordinary Euclidean plane is now frustrated in a way which mimics by many aspects the frustration of icosahedral order in 3D Euclidean space. The model of a monatomic liquid on the hyperbolic plane therefore offers the opportunity to investigate, at a microscopic level, the influence of the degree of frustration, here controlled by the curvature, on the slowing down of the relaxation associated with glass formation.We present the results of the first computer simulation of the dynamics of a liquid in curved hyperbolic space. The hyperbolic plane H 2 , also called pseudosphere or Bolyai-Lobatchevski plane, is a Riemannian surface of constant negative curvature [13,14]. Contrary to a sphere, which is a surface of constant positive curvature, H 2 is infinite: this allows one to envisage the thermodynamic limit at constant curvature. However, ...