Joint system developed in andesitic breccia, shore of Pusan(S.Korea). the size of square is 1mX1m
<a href="//commons.wikimedia.org/wiki/User:Kchwoo9" title="User:Kchwoo9">Kchwoo9</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>