Earlier this year we reported on an unusual project by OPEN Architecture named the Chapel of Sound, which is a planned concert hall in China that's designed to resemble a rocky outcrop. Construction work has been progressing in the meantime and the building has now topped out.

The Chapel of Sound, which is being constructed in partnership with engineering firm Arup, is located in a rural area north of Beijing, near a section of the Ming Dynasty's Great Wall of China . The project is part of a scheme to redevelop and revitalize the area after years of decreasing population.

The building measures 790 sq m (roughly 8,500 sq ft) and will include a semi-outdoor amphitheater, an outdoor stage, viewing platforms, and some additional support spaces. Structurally, it consists of concrete and an aggregate of crushed local rocks, to lend it a natural appearance. The pouring of concrete for the roof recently took place and sounds like quite an endeavor. Construction workers toiled for 24 hours non-stop in shifts throughout the day and night, carefully finishing the surfaces with hand tools as each batch of concrete was poured.

The construction of the Chapel of Sound's roof involved 24 hours of pouring concrete non-stop, with workers working in shifts until the sun rose the next morning OPEN Architecture

"The structure is composed of two interconnected concrete shells," says OPEN Architecture regarding its design. "The outer shell has an inverted conic shape so that it touches the ground with the smallest footprint, minimizing impact on the natural surroundings. The inner shell is shaped primarily by the acoustics, with hard surfaces to bounce off the sounds, and openings on the enclosing surfaces for sound absorption.

"These carefully planned openings to the sky and the surrounding valley also bring in stunning views and muted sounds of nature, as well as dancing sunlight at different times of the day – all orchestrating an ever-changing symphony of nature inside the concert hall. When there is no performance, one can sit there to quietly observe birds singing and insects chirping, gentle breezes rustling through, or rain falling onto the hard floor and quickly draining away."

The topping out of the building concludes the year's construction work due to the coming of winter in the northern hemisphere. Work will begin again in early 2020, with completion expected by mid-2020.