South Korean police say a man has admitted to starting the blaze that destroyed the country's greatest cultural treasure, the Namdaemun Gate.
The gate was the most historic landmark in the capital, Seoul
A fire late on Sunday ravaged the 600-year old wooden structure, leaving only the stone base intact.
Police say the man, a 69-year-old with an arson record, acted over a land row.
South Koreans have been stunned by the loss of the gate, one of the few buildings to survive both the Japanese occupation and the Korean War.
The man, surnamed Chae, was arrested late on Monday in Seoul.
Seoul's southern gate during the 1392-1910 Chosun Dynasty
Constructed in 1398, rebuilt in 1447 and frequently renovated
Some pillars date back to original structure
Named top "national treasure" in 1962
Opened to public in 2006
"The suspect has confessed all of his criminal acts to police," said Kim Yong-su, captain of Namdaemun police station in a televised news conference.
Mr Chae was motivated by a dispute with a development company over compensation related to a land sale and had been convicted of arson in the past, Mr Kim said.
He used paint thinner to start the fire, the policeman said.
The destruction of the historic landmark is a serious blow to many South Koreans.
More than 100 firefighters tackled the blaze
Namdaemun - also known as the Great South Gate - was built in 1398, serving as the main southern entrance into the walled city of Seoul.
The two-storey pagoda which stood on a stone base was the oldest wooden structure in Seoul.
A focal point for tourism in the capital, it had been restored many times but still contained some of the original structure from the 14th Century.
In an editorial entitled "A profound sense of loss", the JoongAng Ilbo daily criticised a lack of care that led to the fire.
"With our history of 5,000 years, the spirit of Koreans and part of ourselves was destroyed," the daily said.
Initial estimates put the cost of rebuilding the gate at $21m (£10.5m).