The vast majority of studies on IP geolocation focuses on localizing the end-users, and little attention has been devoted to localizing the elements of the Internet infrastructure, i.e. the routers and servers that make the Internet work. In this paper we study the maximum theoretical accuracy that can be achieved by a geolocation approach aimed at geolocating the Internet infrastructure. In particular, we study the effects on localization accuracy produced by the position of landmarks and by the strategy followed for their enrollment. We compare two main approaches: the first is more centralized and controlled, and uses well-connected machines belonging to the infrastructure as landmarks; the second is more distributed and scalable, and is based on landmarks positioned at the edge of the network. The study is based on an extensive set of measurements collected using the RIPE Atlas platform. Results show that uniform and widespread diffusion of landmarks can be as important as their measurement accuracy. The study is carried out at both worldwide and regional scale, including regions that were scarcely observed in the past. Results highlight that the geographical characteristics of Internet paths are dependent on the considered region, thus suggesting the use of specifically calibrated models. Finally, the study shows that geolocating IP infrastructure with active measurements is feasible in terms of precision and scalability of the overall system.