Pictured is a carved stone head from Boa Island in Ireland (tinted green for St. Patrick's Day!). The figure, known as a Janus head, has a second face carved in the other direction. The Celtic symbol of a figure looking forward and back is thought to represent transition and the threshold between life and death. More Photos/Info(1).
1. http://radiocarbon.pa.qub.ac.uk/local/fermanagh/Boa/