A $4.1 million art project that has taken 13 years to come into being is finally nearing completion at Hartsfield-Jackson International Airport.

“Flight Paths” by Chicago-area artist Steven Waldeck is aimed at giving travelers a sense of walking through a forest, with a simulated tree canopy, bird sounds and lighting. It occupies an entire 450-foot long underground tunnel between Concourses A and B at the world’s busiest airport.

The installation is now on view for travelers walking between the two concourses in the underground transportation mall, but is not yet finished. Work continues during overnight hours to complete the installation with more components by early fall.

“Passengers walking through the exhibit today will enjoy a more immersive experience after the exhibit is complete,” according to Hartsfield-Jackson spokesman Andy Gobeil.

The airport’s most expensive art project ever produced has gone through a series of twists, turns and delays since it was first selected for the space.

It was originally expected to be completed in 2004 but was postponed amid economic challenges. The budget ballooned from $1.3 million more than a decade ago to a total of $4.1 million, including $2 million for electrical work. Materials for the piece had to be redesigned to comply with current safety codes, and the price increased because of rising labor and material costs, including a conversion from neon to more energy-efficient LED lighting.

Atlanta’s public art master plan calls for setting aside 1 percent of certain spending for art, and the airport has said the installation is paid for with funds set aside from airport-associated fees, such as lease payments by airlines and parking revenue.

Flight Paths is part of a series of installations in the underground tunnels at Hartsfield-Jackson, including the “Tradition in Stone” exhibit of stone sculptures from Zimbabwe between Concourses T and A, and “A Walk Through Atlanta History” between Concourses B and C.