Fort

fort (fôrt) noun: a fortified building or strategic position.
Built in 1783 to defend against potential naval invasions.  The octagonal brick-and-stucco bunker was one of 14 city watchtowers that punctuated the old city wall alongside Khlong Rop Krung. Out of the 14 watchtowers that were built, this is the only one still standing.

In response to WP Weekly Photo Challenge: Structure.