Mandala means circle. In Yoga Quota classes, I'm almost always putting our flows into a circle pattern.
The useful bit about yoga is that you can switch off your brain. But with students who are mostly Oxford students or super busy people, I know that it is very hard to switch off the cita vrtti (whirling mindstuff!) So mandalas help to a certain extent keep you involved and focused on left or right, on a new flow.
What is it about circles?
You can also get these Mandala colouring in books. Lots of the symbols in yoga (and other eastern heritage) are these intricate mandalas. And you can colour in each tiny segment if you like. Well that is also very absorbing!
I personally prefer yoga to do that, but hey, if you have a broken arm and you can't do yoga. Or a cold. Try these for size to get your fix of mandalas!