Many French surveying firms still hold archives on CD-ROMs or old hard drives titled "Projet_ADTOPO_2004.adt". No current version of Microstation or AutoCAD can directly open this. You need a specialized converter or an old Windows XP virtual machine with ProgisCad 2004 installed.
The Powerhouse of Reinforced Concrete: A Look Back at Progiscad progiscad 2002 2004 adcof adfer adtopo hot