A bizarre mountain retreat built on top of a 26-floor Beijing residential building faces demolition after complaints by residents. The rooftop structure is covered by fake rocks, trees and bushes, and can be clearly seen from one of Beijing's busiest commuter roads in one of the city's more upmarket areas. A CNN crew who visited the building on Tuesday saw an official government order stuck to the door giving the owner 15 days to demolish 800 square meters of the structure that have been deemed illegal. No one answered when they knocked. Locals say the unusual high-rise retreat has been slowly taking over the rooftop for years -- construction is said to have started in 2007 -- but is only now receiving attention after images of the unlikely extension went viral on social media.