Do you see that circular feature to the upper right, slightly lighter in color than the surrounding plains? That’s Caloris Basin, the Basin of Heat. It’s called that because when Mercury reaches perihelion, that spot is close to being aimed right at the Sun. It’s one of the worsts spot on Mercury to live, if you’re considering a winter home there. Caloris Basin (formed in some ancient and very large impact) is over 1300 kilometers across — roughly as big as Texas. The mountains ringing it are 2 km high.
Here's a closeup.