that genuine urban explorers "never vandalize, steal or damage anything". The thrill comes from "discovery and a few nice pictures". Some explorers also request permission for entry in advance. Hazards Storm drains are not designed with human access as their primary use and can be subject to flash flooding and bad air. Many abandoned structures have hazards such as unstable structures, unsafe floors, broken glass, stray voltage, entrapment hazards, or unknown chemicals and other harmful substances (most notably asbestos). Other risks include freely roaming guard dogs and hostile squatters. Some abandoned locations may be heavily guarded by motion detectors and active security patrols, while others are more easily accessible and carry less risk of discovery. Injuries and deaths Rooftopping Rooftopping and skywalking are the ascents of rooftops, cranes, antennas, smokestacks, etc., usually illegally, to get an adrenaline rush and take selfie photos or videos. Rooftopping differs from skywalking as the latter is mostly about taking panoramic photographs of the scene below, and safety is more important than the thrill. Rooftopping has been especially popular in Russia.Buildering has a similar goal as rooftopping and skywalking (to reach the roof), but involves climbing the building from the outside rather than infiltrating from the inside. Methods and technology Some urban explorers use action cameras such as GoPro or other helmet cameras for videos. Some also use quadcopter drones for exploration and recording. The location-based games Ingress and the following Pokémon Go based on the former have urban exploration elements. While some are concerned with keeping certain sites secret from the public at large, mainly to prevent vandalism, several apps dedicated to urban exploration exist. See also 24 Hour Fort challenge, an internet challenge which incorporates elements of urban exploration and involves participants attempting to hide inside buildings, often after they close in the evening Dead malls Exploration Jane's Walk List of graffiti and street art injuries and deaths Miru Kim – an artist who documents urban explorations Modern ruins MONU – magazine on urbanism Roof and tunnel hacking Ruins photography Unfinished building References Further reading Timothy Hannem, Urbex : 50 lieux secrets et abandonnés en France, Arthaud, Gates, Moses (2012). Hidden Cities: Travels to the Secret Corners of the World's Great Metropolises; A Memoir of Urban Exploration Tarcher, New York. Margaine, Sylvain (2009) Forbidden Places: Exploring Our Abandoned Heritage (Hardcover), Ninjalicious (2005). Access All Areas: A user's guide to the art of urban