Sinus Concordiae is a bay (sinus) on the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 that lies along the eastern edge of the Mare Tranquillitatis

Mare Tranquillitatis

Mare Tranquillitatis is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt formed in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but...

. Along its northern border is an area called the Palus Somni

Palus Somni

Palus Somni is an area on the Moon of relatively level but somewhat uneven terrain that lies along the northeastern edge of Mare Tranquillitatis and the Sinus Concordiae. It has selenographic coordinates 14.1° N, 45.0° E, and has a diameter of 143 km.The surface of this feature has low ridges and...

, while the southern border is an area of irregular terrain that contains the ruined crater Da Vinci

Da Vinci (lunar crater)

da Vinci is a lunar crater that is located in the eastern part of the Moon, to the northwest of Mare Fecunditatis. It lies along the eastern shore of the Sinus Concordiae, a bay along the eastern edge of Mare Tranquillitatis...

. The selenographic coordinates of this bay are 10.8° N, 43.2° E, and it has an overall diameter of 142 km.