what is the purpose of it?
Prayer and worship
Chapel
A chapel is a Christian place of prayer and worship that is usually relatively small, and is distinguished from a church. 
who built the melbourne castle? Thomas, 2nd Earl of Lancaster when was it built? 1311 - 1322 what rooms can you find in this castle? bakehouse, kitchen, chapel, hall, great chamber, and drawbridge. what are the types of the third one? Bridge chapel, castle chapel, and parecclesion
wiki:5249882
Chapel [SEP] Introduction
A chapel is a Christian place of prayer and worship that is usually relatively small, and is distinguished from a church. The term has several senses. Firstly, smaller spaces inside a church that have their own altar are often called chapels; the Lady chapel is a common type of these. Secondly, a chapel is a place of worship, sometimes non-denominational, that is part of a building or complex with some other main purpose, such as a school, college, hospital, palace or large aristocratic house, castle, barracks, prison, funeral home, cemetery, airport, or a military or commercial ship. Thirdly, chapels are small places of worship, built as satellite sites by a church or monastery, for example in remote areas; these are often called a chapel of ease.