Have you ever ridden a unicycle?  It takes great balance to ride it since there is only one wheel that touches the ground.
I have not. I do not have good balance even when walking so I can't imagine trying to ride a unicycle!
I understand.  I think the unicycle is great.  In fact, they have recently started to be used to create different sports like unicycle hockey!  
That sounds really interesting! It would be fun to watch people trying to play sports on unicycles!
Unicycle hockey
Unicycle hockey is a team sport, similar to rink hockey, except that each player must be mounted on a unicycle to play the ball. A team is composed of five players (plus substitutes), but there is no dedicated goalkeeper role (although one player usually stays back in that position).
The governing body for unicycle hockey is the International Unicycling Federation which publishes the rules for all unicycle sports. The most recent set of rules for unicycle hockey was published in 2015.
The court used
Unicycle
A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a frame with a saddle, and has a pedal-driven direct drive. A two speed hub is commercially available for faster unicycling. Unicycling is practiced professionally in circuses, by street performers, in festivals, and as a hobby. Unicycles have also been used to create new sports such as unicycle hockey. In recent years, unicycles have also been used in mountain unicycling, an activity similar to mountain biking or