Learn how to create a composition by masking with RGB channels
Begin by creating a new blank file. Hit Cmd/Ctrl+N, name it Landmark and set the Width to 480mm and Height to 310mm, Resolution 300ppi and click OK. Now place your sky into the picture.
Add some grass into the picture; mask out whatever sky you’ve already gone in that specific stock image. Press Cmd/Ctrl+T to and click ‘Switch between Free Transform and Warp modes’ in the Options bar, then drag it up. Hit Enter and press Cmd/Ctrl+T again. Now resize and arrange the image.
Hit Cmd/Ctrl+J to duplicate the layer. Move the Grass Copy layer below the original layer and use Free Transform (Cmd/Ctrl+T) to resize and rearrange the image. Repeat these steps a couple of times to add more hills.
Place an Eiffel Tower image into the picture. Ctrl/right-click over the layer and choose Rasterize Layer. Leave only the Eiffel Tower layer visible by holding Opt/Alt and pressing the layer visibility icon, and then go to Windows>Channels, select the Blue Channel, Ctrl/right-click and choose Duplicate Channel.
Click Cmd/Ctrl+L to open the Levels. Drag the sliders until the tower is completely dark. Paint out the extra areas using a hard brush (B) and using the the Dodge and Burn tools (O). Hit Cmd/Ctrl+I to invert. Now you have a mask that can be loaded as a selection.
Click on the RGB to make all the channels active, and press F7. Go to Select>Load Selection. In the dialog box choose Blue Copy and press OK. Now go to Layer>Layer Mask>Reveal Selection. Ctrl/right-click over the mask and choose Apply Layer Mask.
Hold Opt/Alt and click over the Eiffel Tower layer’s visibility icon to make all the layers active. Drag the Eiffel layer below the Grass layer. Press Cmd/Ctrl+T and resize the image. Now go to Layer>Matting>Remove White Matte.
Add your lake image. Ctrl/right-click over the layer and choose Rasterize Layer. Grab the Eraser tool (E), choose a large soft tip and rub out the image around the lake edges to blend with the grass.
Add a selection of houses and trees to create a small community. Rasterize each layer and use the Free Transform to resize and arrange each image. Go to Layer>Matte>Defringe to remove any unwanted parts. Duplicate each tree holding Opt/Alt and dragging the images.
Create a new layer over each hill and the Eiffel Tower by press Shift+Cmd/Ctrl+N. Name it Shadows, set the blend mode to Overlay and check Fill Overlay-neutral Colour. Hit OK.
Keep the neutral layer selected. Grab the Burn tool (O), change the Range to Midtones, set Exposure to 40% and with a soft tip brush, paint the shadows around the hills, under the trees and houses and the tower. Hold the Opt/Alt key to switch between the Dodge and Burn tools.
Use brushes and adjustments to finish off your picture. Add smoke brush strokes to the houses for example, light rays to the sky, perhaps even a Curves layer to finish off.