Artist Tan Draig spent four days weaving the threads around the pillars which support the cast iron structure of Strutt's North Mill in Derbyshire.
Each of the 500 figures is said to represent a worker.
The exhibit in Belper was due to be taken down on Monday but has proved so popular organisers extended the show until mid-July.
Mr Draig said: "The idea of the web is that it reflects the tight spaces that the mill workers worked in, surrounded by machines in great long rows, all running with miles of cotton threads that were being spun, doubled and finished.
"People will be able to walk down the tunnel within the web and see if they can find some of the really tiny figures of workers hidden within it."
The artist worked with more than 100 people on craft projects which have been incorporated into the exhibit.
Strutt's North Mill in Belper was built in 1804 and forms part of the Derwent Valley Mills World Heritage Site.
Hundreds of tiny figures have been hidden in a giant web woven around a former mill.