7Longyou Caves in China
Source: Link
These are 24 caves discovered in 1922.  Magnificent, extensive and perhaps, man-made, the stones have been chiseled from top to bottom. Definitely a result of rigorous labour, experts are puzzled on what could be behind these parallel lines. Moreover, despite its being in existence for 2,000 years, no collapse of any sort is evident and the site is well-preserved. Click the next ARROW to see the next image!
