Perhaps what I find most beautiful and interesting, architecturally, are the roofs. They are very different from what we're used to seeing in the American Midwest.
Tile roofs, much like this roof at Horyu-ji in Nara, are ubiquitous. Newer tiles seem to be made from metal, but many are ceramic. In addition, it's not just the temples and castles that have roofs such as this: houses and train stations even have tiled roofs, and so does JCMU. I've grown very fond of them.
There are many different types of ornamentation on these roofs, as seen here on these tiles at Kinkaku-ji in Kyoto.