The survival of brain tissue in archaeological depositional environments is a very unusual occurrence that has generated much discussion and conjecture forensically. Here, we report the Raman spectroscopic analysis of biomaterial found in the cranial cavity of a decapitated skull dating from the Iron Age, some 2500 years ago, from which the presence of degraded protein consistent with it being naturally preserved brain is concluded. The novel observation of characteristic Raman spectroscopic signatures of biochemicals produced by cyanobacteria, namely carotenoids and scytonemin, both in the brain tissue and surrounding deposits from the cranium is consistent with the waterlogged depositional environment in which the human skeletal remains were found. The Raman spectral data are in support of biochemical, morphological and radiographic analyses of this biomaterial, which therefore can be described as brain that has been significantly reduced in volume inside the cranial cavity. Copyright © 2012 John Wiley & Sons, Ltd.