I don't have a really big area because we are moving house in just over a year, so I cannot make the track permanent (no digging etc.). I would say a tad over 20m x 15m (65ft x 50ft), with part of the area going sharply down. [>:]

UPDATE: I have changed the plans a little to make more use of the space available. I will post these plans soon, along with pictures of the area I have to work with.