The eight-sided structure, buried 14 feet underground, was discovered after almost six months of excavation at Nateshwar, according to officials.
It is the fifth such monument to be salvaged by archaeologists in the last nine years.
An ancient Buddhist monastery, believed to be about 900 to 1200 years old, was unearthed there in 2013. Since then, the authorities have uncovered the ruins of roads, temples and other structures at different times.
Md Abul Monsur, secretary to the Ministry of Cultural Affairs, visited the site on Saturday after the monument was discovered. He said, “Excavation work has been ongoing on 10 acres at the site. We have to take effective steps to protect the discoveries of historical importance.”
Sufi Mostafizur Rahman, a professor of archaeology at Jahangirnagar University, said, "The archaeological discovery from the ancient Bikrampur community has enriched the history of Bangladesh. It will also boost the potential of our tourism industry."