First, create a mountain as usual, by the appropriate icon in the "Create" - click palette. Then go to the "E" in the Shortcut bar next to the mountain to terrain editor to enter. Click above links to "New". The working window is now black. Also below is not no mountain left to see the preview in. Create a large brush to apply a uniform, white surface. The preview is now a square block to realize a fat. Now drag the red point of the column "value" to the bottom. Your brush is now black, which depths are produced. Set the brush to a medium size. In order for the falling water to create the opening, draw a sloping surface from bottom right to center left running. Now it is creating edge rocks around it. First, go to "up / down", in the image of the yellow arrow. If you hold down the mouse button slightly to the right move now, you realize that the white block assumes a slightly grayish color.