Chinese workers tear down the rock garden at the mountaintop villa which is built by professor Zhang Beiqing on the roof of his apartment building in Beijing, China, 16 August 2013. Authorities in the Chinese capital issued an order for the demolition on Monday (12 August 2013), saying the structure was illegal and must be removed within 15 days, the official Xinhua news agency reported. The owner of the 800-square-metre (8, 608-square foot) structure, Zhang Biqing, agreed Wednesday (15 August 2013) to begin tearing it down, the report said, after police and urban management authorities explained that it posed a risk to the public. Xinhua said city officials provided technical guidance Thursday to ensure the buildings structural soundness amid the dismantling as well as to make sure water and electricity did not pose a hazard. Officials ordered that a protective fence be set up around the building so falling objects would not hit passing pedestrians and vehicles. Reports this week drew wide attention to the huge house among what looked like a pile of rocks dotted with trees on top of the apartment building. The rocks, said to be imitation shells rather than solid stone, have trees and bushes growing among them, as in classical Chinese landscape painting. Houses standing on top of multi-storey buildings have been seen before in China, where a rising property market is making land more and more expensive.