A single block of rock rising out of the plain, with nothing around it. Ben Amira — also written Ben Amera — is a monolithic inselberg in western Mauritania, one of the largest still standing anywhere. It is not a mountain built of layers: it is one rock that stayed while everything around it eroded away over millions of years, until it was alone on the horizon. The scale does not survive photographs. You approach and it stays far off; you think you have arrived and there is another hour to go.