This is a mine crater called the Caterpillar...which is at Hill 60, near Ypres in Belgium. Hill 60 is also where the Memorial to the Australian Tunneling Company is located....and also the subject of the movie "Beneath Hill 60". Hill 60 is littered with tunnels, which had begun in 1915 by the British, and was then taken over by the Australians on 9th November 1916.
I really liked this spot, it was quiet & had a real sense of peace about it. I love the line of trees in the background & their reflections in the water that has filled the crater. (I think the water filled crater kind of looks like an eye). The crater is a lot bigger than what this photo depicts...although, perhaps the group of people on the other side of the crater helps put it's size into perspective. Apparently it was originally much bigger than this, but over the years it has slowly filled with debris, soil etc.