When you are about to place a decoration, you will see a green or red coloured border around it. If you see a red coloured border, it means that you are not allowed to place the decoration there as there is another decoration already placed in that area.
You cannot place decorations on top of other decorations, including terrain decorations such as roads, grass or sand.
You cannot place decorations on top of other decorations, including terrain decorations such as roads, grass or sand.