Posidonius
Type: Crater
Size: 96km
Longitude/latitude: 30° E, 31.9° N
Age: 3.2–3.8 billion years
Best time to see: Five days after new Moon (14–15 February) or four days after full Moon (28–29 February)
Minimum equipment: 50mm refractor
is a classic example of a crater sub-type known as a walled plain. It consists of a thin but distinct sits slightly southwest of Posidonius’s centre.