Urbex: Urban explorers reveal the beauty of the abandoned 3 November 2014 Last updated at 12:34 Known as urban explorers, a group of photographers have been entering abandoned buildings in Northern Ireland to document their decaying last moments, producing both stark and affectionate images. The activity, known as urbex, is carried out around the world, and often entails illegally trespassing on private property. Their motto is 'leave only footprints, take only photos' and they say they never cause damage to gain access. The main philosophy is that you don't move anything; you photograph the building as you see it. Change nothing," said one urban explorer, who wished to be known only by his first name, Stephen. Photography expeditions are planned in advance. They usually work in groups of three or more because the buildings are often unsafe, and they might encounter homeless people. The risk of being caught by security guards is part of the attraction, they say. Historic venues including Belfast's Crumlin Road courthouse, before it was burnt out, have been documented. Pictures are uploaded to Facebook and Flickr, for "bragging rights." It's challenging photography because you're looking for colour and patterns in low light. I use handheld torches and long exposures," said Stephen. Occasionally the group are given official permission to enter derelict buildings. Not only do the photos capture the aesthetic of decay, they also raise curiosity over the reasons that lead to the venues being abandoned.