Natural World

Living in the urban area around Frankfurt, there is not so much "natural world" left. Most is somehow manipulated by mankind.
But there are some rare spots that are left to nature. One of them is the dead volcano perhaps a kilometre as a crow flies away from our house.
The caldera is less than 10 metres deep, with a diameter of 20-30 metres. At the bottom (floor) of the caldera is a puddle, some similarities with the Yellowstone volcano :).
The walls (rim) are quite steep, but falling into the caldera is the only danger. No eruption to be expected.
Thanks to Steveng for hosting this Wide Wednesday challenge.