Just yesterday I happened to watch the first episode of BBC's Wild China. The section on caves goes into this, and among other things shows a small village school built inside a giant cave.<p>Here's a picture: <a href="http://static.bbc.co.uk/programmeimages/640x360/clip/p009j8qz.jpg" rel="nofollow">http://static.bbc.co.uk/programmeimages/640x360/clip/p009j8q...</a>
This used to be common in parts of Europe as well, until not that long ago. There are still inhabited houses set into cliffs in parts of France, e.g. around Chinon (<a href="http://www.travelblog.org/Photos/6368827" rel="nofollow">http://www.travelblog.org/Photos/6368827</a>), and some in Italy have become tourist destinations (<a href="http://en.wikipedia.org/wiki/Sassi_di_Matera" rel="nofollow">http://en.wikipedia.org/wiki/Sassi_di_Matera</a>).
There was a guy on 4chan that went crazy and lived in a hole. Later he moved into a cave. <a href="http://4chanarchive.org/brchive/dspl_thread.php5?thread_id=6938187&x=I+live+in+a+hole" rel="nofollow">http://4chanarchive.org/brchive/dspl_thread.php5?thread_id=6...</a>
Not all the cave dwellings have nicely bricked exteriors and modern interiors:<p>[1] <a href="https://secure.flickr.com/photos/sookyeeyap/sets/72157602311169026/with/1512402593/" rel="nofollow">https://secure.flickr.com/photos/sookyeeyap/sets/72157602311...</a><p>[2] <a href="http://yapsookyee.blogspot.com.au/2008/03/ningxia-part-1-dirt-poor-technology.html" rel="nofollow">http://yapsookyee.blogspot.com.au/2008/03/ningxia-part-1-dir...</a><p>(Ningxia - Zhangjiashu village, by Sookyee)<p>The most interesting aspect is how quickly China is changing. Within a single generation, families have moved out of "holes in the mud" to village houses. Satellite TV and mobile phone coverage is also apparently available in Zhangjiashu village (and other similar remote villages).<p><i>Cave dwellings or yaodong still exist for some poorer families. “I used to live in a cave dwelling when I first got married,” said Ma Yan’s mother, Bai Juhua. “Very few people live in one of those anymore. Recently, a few of them collapsed because of the rain. Thank goodness nobody was hurt.” </i><p>...<p><i>They may not have drinking water, no proper toilet, no food…but they will definitely have mobile phones and satellite dishes for their TV.</i>
Still common in Coober Pedy <a href="http://en.wikipedia.org/wiki/Coober_Pedy,_South_Australia#Overview" rel="nofollow">http://en.wikipedia.org/wiki/Coober_Pedy,_South_Australia#Ov...</a>
I would wonder a lot about air quality – radon accumulation or other local equivalents. Might not be worse than fumes and wear traces from other modern building materials, though.