More than twenty types of retinal ganglion cells conduct visual information from the eye to the rest of the brain(1,2). Each retinal ganglion cell type tessellates the retina in a regular mosaic, so that every point in visual space is processed for visual primitives such as contrast and motion(3). This information flows to two principal brain centres: the visual cortex and the superior colliculus. The superior colliculus plays an evolutionarily conserved role in visual behaviours(4), but its functional architecture is poorly understood. Here we report on population recordings of visual responses from neurons in the mouse superior colliculus. Many neurons respond preferentially to lines of a certain orientation or movement axis. We show that cells with similar orientation preferences form large patches that span the vertical thickness of the retinorecipient layers. This organization is strikingly different from the randomly interspersed orientation preferences in the mouse's visual cortex(5); instead, it resembles the orientation columns observed in the visual cortices of large mammals(6-8). Notably, adjacent superior colliculus orientation columns have only limited receptive field overlap. This is in contrast to the organization of visual cortex, where each point in the visual field activates neurons with all preferred orientations(9). Instead, the superior colliculus favours specific contour orientations within similar to 30 degrees regions of the visual field, a finding with implications for behavioural responses mediated by this brain centre.