LONDON, Jan. 10 (Xinhua) -- An art installation has marked the completion of the first phase of restoration work at the world's oldest iron-framed building, cultural agency Historic England announced Thursday.

The new light installation has gone on display at the Grade I listed Main Mill at Shrewsbury Flaxmill Maltings in the county of Shropshire in the UK.

Visible from the street, the artwork called "As Shadows Return" uses silhouettes behind the windows to show workers and machinery inside the mill.

Dating back to 1797, the building operated as a flax mill until 1886 and then as a maltings from 1897 to 1987. It was also a temporary military barracks during the Second World War.

The flax mill used to be referred to as the "dragon on the hill" because of the glow of light and noise of the machinery. It was the largest employer in Shrewsbury and at its peak more than 800 people worked at the mill, including children.

An Apprentice House was built on the site in 1811 to house them, just meters away from the Main Mill where they spent long hours in terrible conditions.

Historic England described the mill's iron frame as truly pioneering, showing how the work of British engineers was determined to overcome the problem of timber-framed mills and factories being destroyed when fires broke out. The design of the mill gave birth to the modern skyscraper.

The installation marks the completion of the first phase of the 36 million U.S. dollar restoration at the mill, funded by the Heritage Lottery Fund, Historic England, Shropshire Council and the Friends of the Flaxmill Maltings.

Work involved stabilizing the building's structure, replacing the roof and unblocking two-thirds of the windows. Much of the mill had been hidden behind scaffolding for more than 10 years.

Commissioned by Historic England and created by Shrewsbury-based and world-renowned light artist Andy McKeown, the temporary illumination will continue to light up the mill until Jan. 31. The lights will be switched on every day from sunset until late and the free installation will continually change for those who would like to go and see it more than once.

The buildings are being transformed into high quality offices for growing creative industries and new small businesses.

Duncan Wilson, CEO of Historic England, said: "'As Shadows Return' is a dynamic and evolving piece to take local people and visitors on a journey through its history."