There is a widely spread myth that Mt. Diablo in Oakland has the second largest viewshed in the world after Mt. Kilimanjaro[1]. With this tool you can actually compare them directly, which is pretty cool:
Mt. Diablo: https://www.heywhatsthat.com/?view=K1JW43D4
Mt. Kilimanjaro: https://www.heywhatsthat.com/?view=ME9CTRPG
1: Debunked here: https://www.kqed.org/news/11808501/does-mount-diablo-have-th...