If you run out of space for new buildings, you'll need to buy town expansions. These are special areas connected to your town and Zoo that you can buy, clear, and use for placing buildings and decorations. To buy an expansion, tap a territory marked with a $ sign and then tap Expand. You might need nails, shovels, axes, and coins to do this. Your town must also meet the given population minimum for you to be able to buy each new expansion.