Game concept
Great Project
The game also links it as Great Projects, Great Project's.
From the game's encyclopedia
Great Projects are massive undertakings that call on all the resources of the Realm.
Some Great Projects involve constructing a Great Building, while others involve recovering from a Natural Disaster.
While the Realm's Ruler oversees the development of the Great Project, Subjects can offer Contributions to assist its progress.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Great Project is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Great Projects are massive undertakings that call on all the resources of the Realm." The game also links it as Great Projects and Great Project's. Patch 1.20.1.2, from game/common/game_concepts/tgp_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/tgp_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.