Cleopatra structure is a 100-km diameter feature having a morphology similar to that of double-ring basins of the Moon and Mercury and dissimilar to that of volcanic calderas on Mars, Earth, and Venus. The 2.4-km depth of Cleopatra is anomalously large compared to venusian and terrestrial impact craters of equivalent diameters. An impartial summary of the situation is as follows: if Cleopatra is a volcanic caldera, it is a strange caldera; if Cleopatra is an impact crater, it is a strange crater. ¿ American Geophysical Union 1990