I worked on a 1.8GB c/c++ codebase, split up on 720 something projects, all making a one monolithic software. There were loads of other code too like python, shellscrips, diverse databases, c#, you name it, you could probably dig it up somewhere.
No one knew half of even a quarter of it all. Some parts were known to many, some parts were feared, some were known to nobody.
Fantastic software but also having some of the most hilarious bugs provoked when developing.
Well painters at that time were definitely chemists.