Mare Undarum (the "sea of waves") is an uneven lunar mare located just north of Mare Spumans on the lunar near side, between Firmicus crater and the eastern limb. It is one of the many elevated lakes contained in the Crisium basin, surrounding Mare Crisium. The selenographic coordinates of this mare are 6.8° N, 68.4° E, and it contained within a diameter of 243 km.
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