At the most basic level a person can get on a horse that is then led through the countryside for hours, Mrs Megaw said , but they can barely be said to be controlling the animal.
She wants to allow visitors to take riding a stage further and try "natural horsemanship" - riding with reins attached to a rope halter rather than a bit in the horse's mouth.
She's also a member of the international Cowboy Challenge, and finds or sets up obstacles for horse and rider to traverse.
The new arena will allow people to get to know their horse over hours or days, as well as riding it.
"Horses have feelings and thoughts. We try and bring that out so the spirit of the horse comes out.
"People need to know how to make that work to their advantage," she said.
River Valley's half-day Grade 5 white water rafting trip is one of the most popular of its kind in the world, owner Brian Megaw says.
White water rafting is the main adventure activity offered at the lodge nestled in a deep valley chiselled out by the Rangitikei River in the remote farming area of Pukeokahu.
The lodge also offers day and multi-day rafting trips, with one starting right up in the river's headwaters and ending at the lodge.
About 4000 people a year take the rafting trips.
A less popular option, also based at the lodge, is a guided day trip high up on to Aorangi Mountain to the west. It's a joint venture between River Valley and the Maori owners of the mountain, the Aorangi Awarua Trust.
Altogether the adventure business employs 10 people during winter, and 20 during summer. Its lodge can accommodate 80 people, with Kiwi Experience buses arriving on 200 days of the year.