https://github.com/davepinch/pinchy.cc/blob/master/content/topics/astronomy/lunar-mare/mare-crisium/mare-crisium.md
Mare Crisium is just visible from Earth with the naked eye as a small dark spot on the edge of the Moon’s face.
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.