The Mourne Wall
This wall encloses a reservoir's catchment area in the Mourne Mountains, Northern Ireland. Built between 1904 and 1922, it is about 22 miles long and runs along 15 different mountains. Every year you can participate to the "Mourne challenge": one day to hike (more like run...) along the whole length of the wall, passing over the fifteen summit (from 332 to 747m / 2451 ft high) and usually having to face the lovely Irish weather conditions (yes yes, June is no better than the rest of the year). But what an amazing place !