Sinus Iridum (Moon)

"Bay of Rainbows."

Sinus Iridum is a plain of basaltic lava that forms a northwestern extension to the Mare Imbrium on Earth's moon. It is surrounded from the northeast to the southwest by the Montes Jura range. (wikipedia entry)

A sinus is a small plain. On the Moon they are named after latin terms describing weather and other abstract concepts.