The spiritual birthplace of the Korean people is a volcano steeped in myth and legend. But with the peninsula divided for decades, South Koreans longing to see it must first travel to China.

The peak -- known as Changbai in Chinese and Paektu in Korean -- and its spectacular crater lake straddle the China-North Korea border.

Small tour buses screech around hairpin curves before unloading South Korean tourists for a short walk to the rim to catch sight of the forbidden North -- and dream of a future as one.

"Unification!" shouted a South Korean man at the site, one of the tens of thousands who make the pilgrimage every year.

According to Korean myth Dangun, who founded the nation's first kingdom in 2333 BC, was born on the mountain to a mother who was transformed from a bear into a woman.

The local tourism bureau says there were about 137,000 overseas visitors in 2013, with more than half said to be South Koreans.

"This place is so sacred," said Choi Byung-Eui, who had journeyed with his father from the South Korean city of Gyeongju.

He paused among the heavy, sustained gusts of wind at the crater's edge that occasionally opened up the thick cloud to allow glimpses of the crater.

"I'm so disappointed and so sad because a lot of people are divided because of the (Korean) war," he said. "Our Korea must be one."

The peak, which stands roughly 2,750 metres (9,022 feet) high, is the highest on both the Korean peninsula and in China's northeast, and is the source of the Yalu and Tumen rivers, which between them mark most of the border between China and North Korea.

The body of water in the crater is known in Chinese as Tianchi, or Heaven Lake, while a few endangered Amur tigers still prowl the slopes and hills of the broader Changbai range.

South Korea spells the name as Baekdu, and a guidebook to China published in Seoul describes it as "more than just a mountain soaring high. It's like a sacred place of national origin."

The volcano has generated headlines in recent years as seismologists warned it could erupt for the first time in centuries, raising alarms over what such a cataclysm could mean for impoverished yet nuclear-armed North Korea.

That country has appropriated the peak's importance in Korean history into its own political propaganda by incorporating it within the mythology of the ruling Kim clan.

The late North Korean leader Kim Jong-Il was officially said to have been born on its slopes in 1942, with hagiographic accounts claiming a double rainbow and new star appeared at the time. Outside scholars say his birth was in the Soviet Union.

When Kim died on December 17, 2011, "layers of ice were broken... shaking the lake with big noise", North Korea's state news agency reported.

Kim's father and predecessor, the North's founder Kim Il-Sung "organised and led the anti-Japanese revolution to victory from there", according to an official biography of Kim Jong-Il.

The Korean name translates as "white-headed mountain", while the Chinese version can mean "eternally white".

The Changbai range spreads through Manchuria, the northeastern region from where the Manchu ethnic group conquered all of China in the 17th century, subsequently ruling as the Qing dynasty for 268 years. Its emperors are recorded making offerings to the mountain.

Gao Shang, a graduate student and ethnic Manchu, said he had wanted to see the crater ever since his parents told him as a child that "there is a magic pool on the Changbai mountain", recalling the tale might even have included a "monster in there".

According to family lore his ancestors came from the area, he added. The mountain "is important for me", Gao emphasised.

Some in South Korea resent China's possession of part of the peak -- five South Korean female athletes at the 2007 Asian Winter Games in Changchun, China held up a sign reading "Mount Baekdu is our land", though they later reportedly apologised after Beijing protested.

Lee Kang-Ho, visiting with his father and son from the southern Korean port city of Busan, was overwhelmed with pride at scaling the volcano.

"It's beyond my imagination," he said, calling the mountain the "lifeline and very root of Korea".

At the same time he was embarrassed that he could not travel through North Korea to reach it, he added.

"I felt shame that I had to spend money in China in order to come here."