Hi,
I work for VIM (vimaec.com) and we specialize in making ridiculously giant Revit projects run smoothly as live projects.
I am looking for Revit projects that are enormous and open source or free to use. Recently I remembered project Soane from an open source competition many years back. This was the ideal project since it was unwieldy in Revit and open source. It opens in about 3 seconds in VIM and runs 180+ FPS.

Do you know of other giant open source projects we could get our hands on? We usually try to find projects that are as big as possible to find out what the limits of our app is, and then go beyond that. So far we can smoothly open Revit projects with LOD500 of 30GB+ (400+ linked files).
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FYI if you're interested in opening large files with great performance, sign up for a trial on our website, we also offer APIs if you want to integrate this in your own apps. We also support 3ds Max and Unity/Unreal workflows.