How to make a really cheap horse arena 40m x 25m?

We are in chch nz, and are looking to make arena for my irish sporthorse to use .We are on a very tight budget.
Update: My horse is rising 3yr old Irish gelding
so I need a secure fence incase he decides to go sideways or refused to turn etc.
He's a giant baby!
Also we want to put a base down ontop of the grass to make it easier on his tendons/legs etc
7 answers 7