How far into a girl's vagina does the hymen sit?

Explanation

The hymen is a membrane that sits some 2-3 centimetres inside the vaginal opening. It is also called 'virginity' because most young girls who have not yet had penetrative sex have an intact hymen. The membrane will always have one or more holes through which the menstrual blood can come out. Not everyone has an intact hymen - tampons, exercise or masturbation can make it burst. Some are also simply born without. The hymen can also be so solid that it needs medical intervention to have it removed. Sometimes it bleeds, though not always.