If you stare long enough while waiting for a train at the Arlington Street Station, you might find some secret images buried inside the often-ignored artwork that hangs on the underground walls.

Recently, a rider standing idly along the Green Line got lost in a picture of sticks and branches, and noticed that tucked in between the twigs were images of Native Americans.

Baffled by his findings, the rider took close-up photos of the artwork and turned to the online community to figure out what was going on.

“What the hell is up with this at the Arlington MBTA station?” asked Matt Karolian, who snapped the photo of the artwork and posted it on Reddit.

Turns out, there is a story behind the hidden images, and the photo of the bundled up sticks that sits on the T’s wall at Arlington Station has quite the history as well.

The image, captured by artist Ross Miller, is part of the MBTA’s station artwork initiative, and depicts “fishweir,” wooden fence-like structures used by Native Americans to catch fish thousands of years ago.

The fishweir was first discovered during excavation in 1913 when the T began building the Green Line underground along Boylston Street.

The Boston Transit Committee documented the findings at the time.

What is now considered Boston’s Back Bay was actually once “a large estuarine bay at the mouth of the Charles River,” according to fishweir.org, which also documented the history of the structures unearthed, following the underground train construction.

The weirs found in Boston were made up of more than 65,000 wooden stakes, buried 30-feet below the ground, and spanned more than 2 acres in the area, the report said.

According to the artist, they were used to catch fish like salmon and alewife (that name sounds familiar, doesn’t it?).

“Buried under Boylston Street and the Green Line subway, fishweirs are direct evidence of the native communities that once occupied the area where urban Boston has grown,” according to Miller’s website.

This might explain why Miller, a visual artist whose work integrates art into the public landscape, decided to embed the images of Native American culture into the photos of the fishweir.

As he notes on his website:

In a city full of bronze sculptures of historical markers and memorials, there is no public display of information about the ancient fishweirs or the people who lived here 250 generations before the colonists arrived. By engaging the imagination with the fishweir story, the Ancient Fishweir Project seeks to expand the time-frame of history told in Boston’s public places and honor the memory of Boston’s early Native inhabitants.

There is more than one photo of the fishweir entwined throughout the Green Line in Back Bay, too.

Miller’s “Ancient Fishweir Project” consists of four, 4-foot-by-8-foot murals located on the Inbound and Outbound platforms along the transit line.

Long an advocate of implementing artwork into station design to “create a friendly and welcoming atmosphere” for riders, the MBTA began putting up art along the T in 1967.

The present collection has grown to over ninety pieces on six transit lines, including the “fishweir” installations.

Here is some of the T’s other artwork that can be found throughout the system: