The L3DT map project file (.proj) is an XML-based file (using L3DT's XML format spec) that lists the files in a map project (such as heightfield and texture filenames), and some pertinent settings (including map size, etc). These project files may be thought of as the main 'document' file used by L3DT.
This format replaces the obsolete '.mgf' format previously used.
See temp1.proj.xml (note XML extension has been appended for wiki reasons)