The roads of southern Japan's Amami Islands used to be lined with walls built from dead coral, but now only a few such remnants of the past remain. During our trip to Amami, we visited the most western village on Kakeroma-jima (the island outlined in purple on this map) and found some of the old walls. Some were quite tall, perhaps two meters.
Nikon D200 + Nikkor 17-55 f/2.8 @ 40mm — 1/125 sec, f/5.6, ISO 250 — map & image data — nearby photos
and lots of sticks
The five sticks seen leaning against the walls in the image above are an example of what one often saw while driving around Kakeroma-jima: long sticks placed at frequent intervals along the road. It turns out that these are for pedestrians to fend off habu, poisonous snakes that are active during all but the coldest months. It was sufficiently cold while we where there that habu were not a worry, but they are a real concern during most of the year, as their bite is excruciating at best, fatal at worst.
When Fumie's grandmother was a little girl, the grandmother's mother lost the use of a leg to a habu bite. One can imagine it was traumatic enough for the one losing the leg, but during those hard times (in the 20s? 30s?), it caused great hardship for the entire family.
I'm not sure how old the coral walls are, but I'd guess at least as old as the trees in the picture above. The picture below, taken further along the road, also gives some indication of the age.
Nikon D200 + Nikkor 17-55 f/2.8 @ 17mm — 1/90 sec, f/5.6, ISO 320 — map & image data — nearby photos