Aztec Pond - Put four small ponds together so they make a square and you will get a massive Aztec pond.
Christmas Pieces - On December 25, you will get them. Alternatively, change the computer's date to December 25.
Desert Pieces - You'll get them on July 4. Alternatively change the date to July 4.
Giant Robot - Place a Large IG tower next to a Radar Station.
Halloween Pieces - On October 31, you will get them. Alternatively, change the computer's date to October 31.
Large Fountain - Place 4 fountains together in a square.
Mansion - Put two red brick houses together.
Space Shuttle Launch Pad - Place 2 Radar Stations together.
The Loch Ness Monster - Place a lake anywhere on the map. Build yellow flowers (sunflowers) all the way around it.