Airborne and satellite remote-sensing surveys of Antarctica have revealed over 400 subglacial lakes beneath the ice sheet. These lakes are one component of a subglacial hydrology network that also includes drainage channels, swamps, and estuaries. The influence of this subglacial hydrology network on ice-sheet dynamics is unclear. Water under ice sheets can reduce friction at the ice-sheet base, and thereby increase ice velocity. Alternatively, partitioning of water into lakes or channels, can also limit the area lubricated by water, and thereby decrease ice velocity. Ice-penetrating radar can map the presence of subglacial water due to the differing electrical properties of an ice/water vs. ice/sediment (or rock) interface at the ice sheet bed. The radar surveys also map constant time (isochronal) layers within the ice sheet that are formed due to chemical (and thus also electrical) differences in the snow deposited at the ice-sheet surface, which is eventually compressed into ice. Burial by subsequent snowfall and ice flow deforms these layers, which were originally surface parallel. Thus mapping these layers reveals the internal stress state and flow history of the ice. Here we report on the internal architecture of the ice sheet in the vicinity of Subglacial Lake Whillans, West Antarctica, as imaged by ice-penetrating radar. In the 2010-2011 austral summer, 500 line kilometers of ice-penetrating radar data were collected over Subglacial Lake Whillans in support of subglacial lake access drilling. In radar profiles (2-dimensional cross sections through the ice), we trace isochronal, internal layers imaged by the radar. Compared to nearby grounded areas, layers in the ice over the lake are highly deformed, suggesting ice-flow disruption over the lake. This interpretation is consistent with the active nature of the lake, which fills and drains every few years, causing changes in friction at the ice-sheet base, and thus non-steady ice flow.