Wat Arun is one of my favorite temples I have visited in my travels around Asia (Japan, Korea, Taiwan, Hong Kong, Thailand.) In my limited knowledge I would say it is heavily Hindu-art influenced. It is very different from the many other beautiful temples of Bangkok. It is extremely tall with very steep and scary stairs that you can climb and walk around high levels of it for a stunning view. The outside is mostly stone and some form of concrete with extremely ornate etchings, carvings, statues, and such. It sits along the river and makes a lovely scene from a boat. You pay a nominal feel of 50 baht (hmm, about $1.50) to enter and can walk around freely. There is quite a nice gift shop too where I bought some traditional Thai color/pattern fabric table cloths for a steal compared to the inflated prices I would pay in Japan for similar items.
I visited this temple twice, once in a rush as a 15 minute stop of a boat tour and once for several hours on an afternoon.
Photo of Bangkok taken from the top of Wat Arun with a telephoto lens.