Conservative Mayor Oh Se-hoon unveiled the plan on Tuesday during a meeting with Korean War (1950-53) veterans at City Hall, commemorating the 74th anniversary of the conflict's outbreak.
City officials said the envisioned pole will display the country's largest national flag, or Taegeukgi, with the lower section featuring high-tech media art, light shows and billboard advertisements.
An "eternal flame" monument will be installed alongside the pole to honor independence fighters and war heroes.
The project, estimated to cost 61 billion won ($44 million), also includes green space and various convenience facilities.
"We aim to create a space with national symbolic significance, similar to the Washington Monument," a city official said.
The height of 100 meters was chosen for visibility from afar, he added.
Gwanghwamun Square, Seoul's main landmark, attracts over 20 million visitors annually, including foreign tourists.
However, the plan immediately sparked controversy. Critics argue the planned addition would be excessive and a waste of money, citing existing monuments to Admiral Yi Sun-shin and King Sejong the Great in the square.
