The 12ft (3.66m) metallic pillar first appeared in the DRC's capital, Kinshasa, on Sunday morning, and by Wednesday morning locals were taking selfies with the installation.
But footage from later that day showed crowds destroying the monolith with sticks and fire.
Residents say they saw people digging a hole at the location on Sunday.
"On Sunday morning, I got a call when I was doing some sport to tell me they found something strange. I came and I said: 'This is cultural, it's extraordinary,'" said neighbourhood mayor Thierry Gaibene.
The pillars have been seen across the world.
Conspiracy theories have emerged around the monoliths, including comparisons to Stanley Kubrick's 1968 film, 2001: A Space Odyssey.
Kinshasa local Serge Ifulu said: "We woke up and saw this metallic triangle.
"We were surprised because it is a triangle that we often see in documentaries about freemasons or illuminati."
In August last year, a mysterious objected parachuted into dense jungle in the north of the DRC.
Two people were arrested and questioned until Alphabet, the company which owns Google, said the device was an internet balloon.