Sentence:  [E]ach tower, except those at Santandria and Sargantana Island, had a <WSD>machicolation</WSD> over the entrance. In the larger towers this <WSD>machicolation</WSD> was supported by five or more corbels while the smaller towers had a smaller <WSD>machicolation</WSD> supported by four corbels. 
Meaning of the word marked with <WSD> tags:  A projecting parapet with a series of such openings.