One hundred years ago today, a meteor exploded above Siberia, flattening trees over an area of a couple thousand square kilometers (one-tenth of Wales). This video shows the mostly recovered forest, and a view of the lake that might or might not be an impact crater:
The narration overstates the "mystery" about the cause of the explosion. We might not have any of the traditional tell-tale signs of an impact, like a crater or even a bit of leftover meteorite, but we've observed smaller atmospheric meteor explosions. People are still floating alternative hypotheses, but there's little reason to think that this wasn't a case of smashing-from-space. Scientific attention has turned towards the details of the impact: Was Lake Cheko a result of the event? Where did the meteor come from, how big was it, and are we more doomed than we thought?