The Drusus Stone looks like a giant acorn, and for a reason. It is only the core of a Roman monument. By the Middle Ages, its outer stones had been taken for other buildings, and what remained became known as the Acorn Stone.

It honours General Drusus, who built 50 forts along the Rhine and led campaigns between 12 and 9 BC. He was popular with his troops, and when he died after falling from his horse, his brother Tiberius had his body brought to Mainz. His camp here took the Celtic god Mogon’s name, Mogontiacum, which slowly became Mainz.

VoiceMap’s Roman Legacy tour stops at the stone in the citadel grounds to explain its acorn shape and the general’s death.