Grjótagjá caves near Mývatn lake, Iceland
<ul><li><a href="//commons.wikimedia.org/wiki/User:Chmee2" title="User:Chmee2">Chmee2</a></li>
<li>derivative work: <a href="//commons.wikimedia.org/wiki/User:DerHexer" title="User:DerHexer">DerHexer</a></li></ul>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>