Clavius - 231 km wide
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This crater is so big that its rim is acutally a circular ring of mountains. It is 3.9 billion years old. Its flat floor is home to many smaller newer craters. Clavius is in the middle of the southern highlands. This is old rough country that was never flooded by lava. Although its soil is ancient, it is lighter in colour than the lava of the maria. (The older anything is on the moon, the darker it becomes due to continuing bombardment by micro-meteorites.)
Image: February 07, 2006