Dangling on ropes 150 metres in the air in the desert heat, six young men are systematically washing down the 12,500 glass panes that clad the Abu Dhabi National Exhibition Company's (Adnec) striking Capital Gate centre.
Not a job for anyone with a fear of heights, the precipitous descent involves clinging to the underside of the world's steepest man-made tower using specially designed suction cups. Meanwhile, a team at the bottom of the tower has the less terrifying task of hosing down the lower floors from a moving platform.
It takes the team 30 days to wash the entire building. And the moment they finish they have to start again.
"We have to use a variety of techniques to clean our buildings, from rope access to boom systems, gantry systems, cradles and spraying with high-pressure hoses," says Alain El Tawil, the managing director of Grako, the company in charge of cleaning the tower, which leans at an angle of 18 degrees off vertical. It is also responsible for keeping the Burj Khalifa gleaming as well as a host of other oddly shaped and difficult to clean edifices.
With some of the world's tallest and most bizarre buildings, the Middle East has become a study in the art of the possible. For window cleaners, it's becoming more and more of a challenge to keep up.
"Each company wants to build something different," says Mr El Tawil. "And that means making their buildings bigger and more complicated. Over the last eight years we have seen the company grow by 100 per cent each year in terms of staff numbers and we always have to keep recruiting in order to meet the demand."
Mr El Tawil's firm is not the only one challenged by the growth of bizarre building design. The struggle to maintain such structures is a problem faced throughout the construction process.
"As tall buildings grow more sophisticated, systems to maintain them are increasingly addressed in the initial designs. Architects need to determine how workers will handle issues, where materials will be stored and how crews can move around the building without affecting tenants," says Kevin Brass, the public affairs manager at the Council on Tall Buildings and Urban Habitat, a think tank based in Chicago.
"In buildings, space is always at a premium. Anything that takes up rentable space slices in to the economics of a building. As buildings grow taller, the designers spend an extraordinary amount of time determining where to locate the mechanical apparatus," he says.
The trend is big business for Theo van der Linde, the operations manager for CoxGomyl, a company that specialises in installing the gondolas used to clean many tall buildings. As a rule of thumb, the more complicated and bizarrely shaped the building, the more work for specialists such as Mr van der Linde.
"We work from the start with the architects who will be doing the overall design of the building and then assist them to ensure that the building maintenance units can reach all areas of the building to do cleaning or maintenance on the facade," he says. "Our specialist design team then design the gondolas according to the geometry of the specific building. The actual cleaning process is conventional using water, detergent and a applicator with the window wiper to remove the access water, the same as what they will do when they clean your car windows at the filling station, except that it is a few hundred meters above ground level. Whoever is going inside the cradle needs to have an aptitude for heights."
Facilities management companies, too, say the job is getting more demanding as the shapes and sizes of buildings become ever more complicated.
"We use a number of techniques to carry out facade and roof cleaning, including abseiling or rope access, man-lift equipment, suspended platforms and, finally, cleaning from the ground with a water-fed pole system," says Mark Cooke, the general manager of business operations in the Middle East at the facilities management company UGL.
"It depends on the type of buildings and the possible accessibility for facade cleaners to conduct their cleaning. Each building is treated individually, which includes a risk assessment and a safe work method statement."
So how much does all this cost? Mr El Tawil says an average tall building can cost anything between Dh30,000 (US$8,167) and Dh60,000 per cleaning.
A large part of that relates to the access requirements and the skill sets, training and the certification required in carrying out the cleaning, says Mr Cooke. Labour costs and the level of safety standards adhered to are also important. Window cleaners and their managers can earn anything between Dh1,500 and Dh25,000 a month.