According to Lonely Planet (which often needs to be taken with a grain of salt, but in this case offers a highly plausible explanation), Chinese ships used to come to Bangkok carrying tons of old ceramics as ballast. This ballast was used to particularly good effect in the early 1800s (long before anyone thought of the term "found art") at Wat Arun. I don't know if the scale comes through with this image: the top of this thing is 82 meters above the ground. For those not familiar with the metric system, read "bloody huge."
I had returned there today to take pictures, and to attend a meditation class, but I was the only student and the teacher (Har Tanto, mentioned yesterday) didn't show up. I have his phone number, so I'll check next time - it's supposed to be every day. I'm wondering about returning though: classes are outside at dusk, and the area seems to be a breeding ground for mosquitoes. I might do better to find another place to study.