Browhead Signal Station, Mallavoge, Co. Cork

Weatherboarded in timber-effect slate to shed rain from its rubble stone walls, the building rises two bays wide and three storeys, with bartizans, small overhanging turrets originally intended for defensive lookout or musket fire, projecting from three corners and again from the south elevation. The roof is flat concrete with a rendered chimneystack, and square-headed windows and a door punctuate the walls, all enclosed within a rough stone perimeter wall. It is now a ruin, but an unusually complete one, and that completeness is what makes it worth pausing over.

The tower belongs to a chain of signal stations run up around Ireland's east, south and west coasts at the start of the nineteenth century, a defensive network built in direct response to the shock of 1796, when a French fleet under Hoche and Wolfe Tone reached Bantry Bay and came close to landing an invasion force. The near-miss galvanised the British administration into building visual telegraph stations at regular intervals, each within sight of the next, so that a warning could be relayed rapidly along the coastline by flag or semaphore. Browhead's tower was already half built and weather-slated by September 1804, and construction was finished within the year, by the following September. What makes the site more than a single military relic is its neighbour: the remains of a wireless station built here by Marconi's company in the early twentieth century, along with an associated watch station. The two structures sit within sight of each other, separated by barely a hundred years, and between them trace an entire arc of how information was moved along this coast, from a soldier reading semaphore flags with a telescope to a wireless operator transmitting messages through the air by radio wave.

That juxtaposition is the real interest of the place: not a single tower but a small cluster of buildings representing two completely different eras of coastal communication, stone and signal flag giving way to aerial and radio wave, standing on the same exposed ground.