This essay takes stock of large dams and their reservoirs as a tectonic collective, as an aggregated entity widely distributed in space and time. The global geography of large dams is lumpy, dynamic and migratory. Touring this infrastructure we encounter anthropogenic collision spaces where contradictory and extreme forces coalesce. We find dams and their extensions ever more hybridized with the fish that they endanger. We see exponentially accelerated erosion and post-peak soil accumulating in giant reservoirs, preventing sediment from reaching the sea. We investigate this collective experiment, watching it form new associations as it comes of age.