The Moon’s surface is covered with flat, circular sunken areas known as craters. Some craters like Clavius are so big that they can be seen even without the help of a telescope. Clavius is 235 kilometres wide and is surrounded by huge mountains. Some craters however, are very small in diameter.
The arrangement of mountains around a large crater is peculiar; they form a circular wall. These mountains slope down gently towards the outer surface while they form a steep slope inside. When Galileo first observed craters, they looked like cups. He named craters so from the Latin word for cup.
Picture Credit : Google