Buy construction rights outside of your land and immediately adjacent. Build a path in the air over that piece of land, and then lead it downwards to a main path in your park. Leave the path building window up. When lots of people are on the path outside your park limits, delete the path that they are walking on. They will fall onto the ground outside your park and will be stuck on one square of land. Note: Do not pick them up if you wish them to stay there.