Mandalas are very inspiring! Something about the symmetry and colors just seem to click. It's easy to see why they've been used in many different cultures and religions for bringing the mind into focus. And there's something really cool about their randomness - changing where you put each color just slightly results in a totally different piece.
I've played around with different ways of tie dying mandalas and always have had fun with them, but have never approached anything like the mandalas of Courtenay. But then he's been making them since 1968! His website has an amazing variety - you can spend blissful hours looking at all his work.