Your face is reflected in the black mirror, but you can't see yourself clearly. Your features swim in and out of view, like a vision in smoke, in one of the eeriest objects (and that's saying something) in this autumn's sensational blockbuster at the British Museum.
It is easy to imagine why mirrors like this, made from a highly polished sliver of the dark mineral obsidian, were coveted by magicians in Renaissance Europe after the conquest of the indigenous American civilisation that made them. There is an occult quality to the image of yourself that materialises for a moment, making you wonder exactly who you are. Did Moctezuma, last ruler of the Aztec empire, suffer that same anxiety when he gazed into his black mirror? It was said he saw disturbing omens there – signs of strangers coming. Premonitions of imminent catastrophe.
The black obsidian mirror captures the mystery and tragedy at the heart of the British Museum's new exhibition. Moctezuma's story is one of absolute power – and abject surrender. The real emotional power of this show comes at the end, when you see the armour and banners of the Spanish soldiers who destroyed this ruler and his world, and are confronted with a detective puzzle. Why did he make it so easy for them?
But this is what really makes him think, as he ponders the violence of the concrete jungle:
Moctezuma's passive acceptance of Cortés suggests he simply didn't see the use of fighting. Maybe he was a wise ruler doing his best for his people by urging them not to waste their time against impossible odds. Obviously that was never going to get him a reputation as a Mexican national hero.