The W Road winds up Signal Mountain, and people who travel it often know the twists and turns of its hairpin curves.
Something they are not used to, however, is the sight of bright blue icicles.
"Oh I stopped the car. I took pictures of it. Everyone behind me stopped their cars and took pictures of it," said Sarah Campbell, who lives on Signal Mountain.
Matthew Hilliard pulled over to take pictures too.
"It's bright blue like the sky," said Hilliard. "I've never seen that before."
Campbell says she posted it on Facebook and she has been getting a lot of comments.
Some of her friends think it's a prank.
"They think people are using food coloring. People are obsessed with that theory. I really don't know if it's true or not," said Campbell.
We decided to take a sample to Dr. Michael Dabney, an analytical chemist at UTC.
He didn't rule out the food-coloring theory but he observed it wasn't just blue on the surface; the color was well-distributed.
"My first knee-jerk reaction would be to say there's some sort of dissolved mineral," said Dr. Dabney.
Dr. Dabney told NewsChannel 9 the intense blue color is typical of certain copper compounds.
"I have seen it before, generally in areas where there used to be old copper mines," said Dr. Dabney.
He says it's possible that acid rain could be eating away the front of the mountain, exposing areas that normally wouldn't be accessible to water.
"I would say it's definitely safe. It's the same sort of runoff we get off the mountain on a daily basis whenever it rains in Chattanooga," said Dr. Dabney. "It's just at this point, because it's frozen in time if you will we can actually see it occurring."
Dr. Dabney held onto a sample for us to run some tests.
Whether it's dissolved copper or not, W road drivers are enjoying their own winter wonderland.
"Everyone thinks it's pretty cool," said Campbell.