Central Peaks
Some Central peaks of craters rise over 6,000' and is one of the things I look for when viewing the moon. You can tell how high the central peaks are from observing the length of the shadows they produce especially near the terminator.
Central peaks are formed from uplift of the surface at impact and I think some material from below the crust ends up as part of the formation of the peak. The height is probably do to the low gravity on the moon and the size of the impact.