Wikipedia says that Great Pyramid of Giza took 27 years to build. Long time, but I wouldn't call it generations. Smaller pyramids presumably were faster to buil

Wikipedia says that Great Pyramid of Giza took 27 years to build. Long time, but I wouldn't call it generations. Smaller pyramids presumably were faster to build. Cathedrals might be more typical example of centuries long projects, although for me its not clear how expansions and renowations are delineated from initial construction