Mare Crisium (Wikipedia) Mare Crisium /ˈkrɪsiəm/ (Latin crisium, the “Sea of Crises”) is a lunar mare located in the Moon’s Crisium basin, just northeast of Mare Tranquillitatis. Mare Crisium is a basin of Nectarian age.
Mare Crisium is just visible from Earth with the naked eye as a small dark spot on the edge of the Moon’s face.