My favorite tool for visualizing a codebase is Gource. Here's a 1 minute visualization of the Linux Kernel repository from 1991-2015 https://twitter.com/mattrickard/status/1423366779590430721
Here's a render I made in December, "1500 Commits (39 months) in 1 and a half minutes": https://www.youtube.com/watch?v=szhYhph4C2U
And he's another one I made a few years ago, "100 Commits (18 months) in 1 minute": https://www.youtube.com/watch?v=aIN4mOdL0d0