Random Structure Appeares in-game

I decided to make a map for testing mods, but the map looked too good to be destroyed by bombs and nukes, so I used it as a survival map instead. After playing on the map for about 2 hours I found a small strange little structure in the desert biome not too far from my spawn (which I did not build). I couldn't find an answer on the internet so this is the reason I am posting this article. The only mods I used were the single player commands mod, and the more pistons mod featured by the Yogscast. I am looking for an answer or something along the lines of that. Please comment if you know anything about this, it would be appreciated.

Where I found it

Game version- 1.1 maybe? or 1.2.4 or 1.2.3, probably 1.2.3

Seed- 1173333689506127087

Co-ordinate x- -184.95 (roughly)

Co-ordinate y- 83.62

Co-ordinate z- 242.10