When you are about to drop the decoration called "park pond" into place (which is in the trees group of decorations) it has arrows on 3 sides indicating that you should be able to drop a second one in the adjacent square next to it and have the two join together like the creek decoration or like roadways do. However, while I am able to make roads and the creek automatically join up into one thing, when I try it with park pond I just get two separate ponds with a thin line of grass in between. Does anyone know how to make this decoration join together?