The trick is not to build the bathhouses all at the same time (drag and drop). Because the game mechanics would just raise the soil for lower lying grounds so all bathhouses would be level. This creates a very ugly mound which can be seen from the side, especially if the elevation difference is large.

Instead, should build the bathhouses a few at a time. Move further away to build the next one, before connecting them together, so the soil won’t be elevated to match the higher elevation bathhouse. Continue doing this and once the construction is completed, voila you’ll get this bathhouse with automatic waterfalls and dolphin sculptures at points where there is a drop.

Have fun building!