i thin it is The diagonal
An indoor riding arena is an indoor area where you can ride horses.
in an indoor riding school you can not do a perpendicular
The perpendicular
It only depends on how small the indoor is. If it is large you can do any figure in an outdoor ring.
The perpendicular.
National Indoor Arena is an indoor arena in United Kingdom and was opened on 1991.
You could, but outdoor arenas are often called menages, an indoor arena can be called a indoor school, or an indoor arena.
It is an 18,000 seat indoor arena...
Podium Arena is an indoor arena in Poland and is is under construction.
While riding in at a riding school either in an indoor or outdoor arena people are expected to pass left to left. Anyone going at a faster gait has the right of way. Slower riders should move towards the inside track and not ride on the rail.
Arena Armeec is an indoor arena in Bulgaria and was opened on 2011.
SAP Arena is an indoor arena in Germany and was opened on 2005.