A strategic infrastructure project in Rome, Italy, and namely the Metro C line, is presented here for scrutinising how institutional frameworks and governance arrangements shape megaproject implementation. On the one side, we look at legal endowments and institutional reforms related to a still incomplete territorial rescaling; on the other side, at routines and practices among actors in project management. More precisely, we develop these two fundamental acceptations of the institutional, reconstructing the management of the project and the path of Italian downscaling reform still underway (that has implications for the governance of projects too). Both these realms have been affected by the advent of the Legge Obiettivo, the special law that for fifteen years has been governing strategic projects in Italy-Metro C included. Via a review of regulatory measures, relevant theoretical constructs in the fields of governance and project studies, and with the help of a number of interviews conducted in 2016 and 2017, we delve into the main reasons that explain the Metro C implementation failure as to cost overrun and delivery delays, and found the primary causes of these latter in the fragmented public client role that cannot guarantee the project's governability.