In medieval times, should intruders battle their way across a drawbridge and find themselves in the main gateway of a castle, they would often have to deal with Murder Holes. These holes, usually four to six in number, are located in the roof of the main gatehouse. Sometimes though, they can be seen in the curtain walls by means of an extended platform or projecting parapet of a castle.
Once the intruders had entered the gatehouse, they were defenseless. Poised above, the archers would rein a flurry of arrows below. At the same time, soldiers would drop heavy stones, boiling water, molten lead or tar. Occasionally, excrement and even the odd dead body would also be tossed from above - obviously to intimidate and disgust the attackers.
These particular Murder Holes are in the gatehouse at the magnificent Castle of Caernarvon, in North Wales.