Different angle showing that the annex is in fact underground, hidden away inside the mountain... without having to excavate to the surface. The entire colony could be placed this way, but I had limited room between the cliff face and the aqueduct that was 

 

 

 

Feeling like on Dagobah, searching for Yoda 

 

 

Construccion colonia (Dia 6) 

Halo 4 Battle Riffle (V.3) This one isn't too small or too big like the V.1 & v.2 --> success 

Shut up and take my money!