Nearly all these sites have been managed or maintained by Jesuits at some point of time since the Society's founding in the 16th century, with indication of the relevant period in parentheses. The Jesuits built many new colleges and churches over the centuries, for which the start date indicated is generally the start of the project (e.g. invitation or grant from a local ruler) rather than the opening of the institution which often happened several years later. The Jesuits also occasionally took over a pre-existing institution and/or building, for example a number of medieval abbeys in the Holy Roman Empire.