They came out onto the top of the old stone curtain-wall that joined Broad Arrow Tower to Salt Tower on the south. Arm in arm, they strolled along the battlements. To the left they could look across the moat – an artificial oxbow-lake that communicated with the Thames – and a defensive glacis beyond that, then a few barracks and warehouses having to do with the Navy, and then the pasture-grounds of Wapping crooked in an elbow of the Thames, dim lights out at Ratcliff and Limehouse – then a blackness containing, among other things, Europe.