The Moon stage is the seventh stage in Hill Climb Racing, and costs 175,000 coins to buy. Early in the game, it is the best stage by far for earning coins, due to it's low gravity, which makes performing flips and achieving air time easier. It has the lowest gravity of any stage, but it is not always a convenience.
As stated above, Moon has low gravity, which makes flips easier. Its actual landscape is a combination of Arctic an Countryside, with steep hills and jagged outcrops, but it is rarely seen because of the amount of air time that can be achieved. While flying in the air, however, it is easy to miss fuel cans and will likely be the reason most people lose. Any vehicle can work on this map, but the quad bike and Monster truck are amazing when it comes to flips because of their powerful engine and four wheel drive.
You can use the Moon Lander to fly up using the low gravity and use the air time to make quick money (around 20k per run)