Great Wall Lichens:The Great Wall at Mutianyu, Beijing,  China. The wall was first built during the Northern Qi Dynasty (550 - 557) and then later rebuilt in the Ming Dynasty (1368 - 1644). Dry and irradiated by harsh sunlight, for the most part it appears to be inimical to life.  During a persistent search however, I find a number of small shaded microclimates in which communities of lichens thrive. It's tempting to believe that, these are as old as the Great Wall itself.