The wide open world awaits.
Grass
Grass is a normal, empty tile, just waiting to have something built on it. Road construction is like interior decoration, you know? You just have to fill empty space. It’s okay, nobody was using those wide open spaces anyways. We’d show you a picture, but we don’t want you passing out due to boredom and end up getting keyboard-face.
Farm
Unless you want to build right over them, farms are great places! You can grow crops, raise cows, and park a cute pink tractor next to your home. Wait, a pink tractor?
Rocky
Rocky terrain is full of pebbles, rocks, stones, and boulders. The sort of thing you would definitely not want to stub your toes on. Rocks are serious impediments to roadbuilding, so you will have to take time to bulldoze them before you can keep going.
Rubble
Rubble is what’s left over after you’ve blown something up. It’s only marginally less attractive than forests and wetlands. You have to bulldoze it to clear it out before building over it.
…
But no, they’re still pretty much used for getting over stuff.
Trees
This is where cute, pink, fluffy bunnies live. Revolting, isn’t it? You can pave it over with a road for twice the normal cost.