Xemxzija Support Defence Post is a single storey blockhouse on the cliff overlooking the main road from St Pauls to Mellieha. There are two machine gun loopholes overlooking the road to the North-East. The observation tower has been expanded to the rear to give two additional observations windows.
It is assessed that this would have be a Support (L) Defence Post, with excellent views of the Mistra Bay area and road leading from Mellieha.