Introduction to Pigeon Depression: is the habitat of mountain pigeons. The bottom of the depression is shaded by green grass and scattered with flowers. A curve of clear water reflects the sky and penetrates the ground, gurgling and echoing with crisp sounds; several stone buildings, The arrangement is orderly and the layers are clear; a group of mountain pigeons fly out from the stone building, hovering overhead, drawing a black arc and a trajectory of vigorous life in the blue sky.