This is kind of quirky thing, but one I ran across and found fascinating.  Messenger pigeons have been used since ancient times for communication across long distances. Of course, whatever message has to be written small on a tiny piece of paper or the pigeon couldn’t carry it. Still, they have provided an invaluable service for many thousands of years.

“Homing pigeons (Columba livia) can reliably deliver a short message from any location within a roughly 400-mile radius to their home base. Even today, information carried by homing pigeon can still compare favorably in speed and reliability with information carried by Internet.” http://www.helium.com/items/2380155-carrier-pigeons-through-history

A great summary is here:  “The first known use of pigeons as postal messengers was in ancient Egypt. In 2900 B.C.E. in Egypt, incoming ships released pigeons as an announcement of important visitors. Around the time of Moses, the Egyptian army used carrier pigeons to deliver messages. In 2350 B.C.E. King Sargon of Akkadia—the present Iraq—ordered each messenger to carry a homing pigeon. If the messenger was about to be captured, he released the pigeon, which flew back to the palace. Its arrival meant another messenger should be sent. Pigeons also bore messages in ancient China, Persia, India, and Greece, where the names of Olympic victors were carried back to their cities.

During the Dark Ages the Arabs established regular airmail pigeon courier services. According to one tale, a caliph in North Africa satisfied his taste for Lebanese cherries by having pigeons fly them in. Each carried one cherry inside a silk bag. It was the first parcel post. Reportedly, a prize pair of carrier pigeons in the Arab empire could fetch one thousand gold pieces.

During the Crusades Richard the Lion Heart’s men captured a pigeon that carried a message reporting that a Moslem army would arrive in three days to break the Christian siege of Ptolemais. A forged message was substituted, saying that no help would be coming. The besieged town surrendered. The Moslem relief army arrived to find the Christians solidly entrenched.

Pigeon post was the world’s fastest communication system for all the centuries of the Dark and Middle Ages, and remained so until Samuel Morse’s invention of the telegraph in 1844 and Guglielmo Marconi’s invention of radio in 1895.” http://www.mediahistory.umn.edu/archive/pigeonpost.html

Medieval dovecotes are found all over Britain. The birds provided a valuable controlled food source, as well as a source of saltpeter for gunpowder starting in the 17th century.  http://www.archaeologyuk.org/ba/ba35/ba35feat.html  http://www.buildinghistory.org/buildings/dovecotes.shtml

The cave system under Carreg Cennan Castle is another example:

The most exciting feature at Carreg Cennen Castle awaits exploration at the south east corner of the inner ward. Here a steep set of steps leads down past a postern gate into the bowels of the castle, and beyond into a damp limestone cave. Your footing may become unsure as you travel deeper inside, and torches are a necessary aid, for the exterior world rapidly falls away into complete darkness. The bedrock is cut by several of these natural fissures, but only one was modified for use inside the castle. Much of the passageway was carefully lined with stone and the ceiling vaulted. A series of pigeon holes was built into the wall, forming a dovecote (to breed a winter food supply, or possibly to house homing pigeons).  http://www.castlewales.com/carreg.html

Or for a video of my trip there:  http://www.sarahwoodbury.com/carreg-cennen-castle/