Radio galaxies are important objects. They are associated with the most massive black holes and thus with the most massive galaxies, and they are often located in clusters of galaxies. Studying radio galaxies at z>1 not only allows us to get insights on the mechanisms responsible for launching their powerful relativistic jets, but also to better understand important aspects of the formation and evolution of massive galaxies and clusters. In this talk, I will focus on the latest results from our successful HST snapshot survey of 3CR radio-loud AGN at z>1. We find strong evidence that galaxy mergers (and possibly black hole mergers) are intimately tied to the triggering mechanism for radio-loud AGN activity, while the same may not be true for other AGN types. The Mpc-scale environment of high-z powerful radio sources also shows interesting features when seen with HST. A significant number of these objects are located in rich groups/clusters, which may be showing the process of formation of the galaxy red sequence. Finally, I will present the case of an offset quasar that can be explained as a result of the gravitational wave rocket effect following a supermassive black hole merger.
