One form, known as grottes sepulchrales artificielles in French archaeology, are dug into the earth.[8] The second form, which is more widespread, are known as cryptes dolmeniques in French archaeology and involved the chamber being erected above ground.[8] Many chambered long barrows contained side chambers within them, often producing a cruciform shape.[9] Others had no such side alcoves; these are known as undifferentiated tombs.[9]