Under the lasting influence of romantic-mystic views of the 19th and 20th century the function of a crypt within the structure of a church is still a matter of false interpretation. This book discusses on basis of a broad range of examples which were erected during the 11th and 12th century in Italy the possibile use of this building type. The crypt is embedded within a clear structural system and hierarchy of the whole church structure even though its functions are different.