> As a non-mathematician, the last truly big mathematical project that caught my imagination was Hilbert's attempt to found all of mathematics on a firm founda

> As a non-mathematician, the last truly big mathematical project that caught my imagination was Hilbert's attempt to found all of mathematics on a firm foundation of logic. The classification of finite simple groups aka The Enormous Theorem might also interest you. It is around 10,000 pages spread across 100s of journal articles by ~100 authors over a 50 year period. https://en.wikipedia.org/wiki/Enormous_theorem https://en.wikipedia.org/wiki/Enormous_theorem You could jump to the history section if you want to skip some technical parts. There have been other huge programs but they might be harder to describe without a lot of jargon.