Down below in the wadi, you see the riverbed disappear into a cave. A Belgian speleological expedition recently explored the cave — after 2km of walking it, they dived for a further 6km, but never found an end to it. Socotra is in fact riddled with caves: it's a huge chunk of karstic swiss cheese jutting out of the Indian Ocean
Wadi Geneb is not on most visitors' itineraries. I heard about it only because I am Belgian myself, and my guide had also helped the Belgians get to Wadi Geneb, so he brought it up in conversation. I knew right away I'd have to go see it for myself.
Above this location, you see a appears to be a massive boulder, topped by a lone tree. It is in fact a huge boulder, and it overhangs the entire valley. On Google Earth, you see that the thing simply broke loose from the cliff-face, and now teeters over the valley. Yes, I did quicken my step as I skirted it on the way back to the road.