神秘人行道事件

from http://liuzhou.blog-city.com/things.htm

O.K. I give up. What is it?

I've come across two of these things now. They are about 6 inches square and set in the pavement (sidewalk).

补充说明：事件发生地点在广西柳州

没有人知道是什么吗？

不知道。

行为艺术，远古文明，还是外星来客？

老外喜欢大惊小怪。和我一样。