Turk's Cap Cactus (Melocactus ssp?, 花座球属).
I found it growing through a crack in a wall, in one of the more rundown parts of Hulishan Cannon Fort in Xiamen. It is not a native species to China, and one wonders how it got here; When did its progenitor come from the Americas and how did its seems come to that particular crack between two sturdy stones?
