Putin has a secret $1B palace in Russia that is funded by corruption. This video by Alex Navalny goes into detail about how it's funded, shows drone photos from the outside, and uses a blueprint they acquired/verified from one of the architects to do a 3D reconstruction of the interior.
The video is about 2 hours long, lots of details about Russian politics and Putin's history. Shorter summary is here: https://www.youtube.com/watch?v=n8J2dW-QYQY