Baekdu-san
the sacred "White-Head Mountain" of the North
Left: The peak from above, frozen in winter,
with the Chinese name of Cheonji Lake
displayed, from a geography website.
I have not yet been there; these images are from North Korean tourism brochures.
Cheonji-ho in the winter, a sight few people ever get to see   (KNTO photos)
The Korean name Baekdu-san / 백두산 / 白頭山 means "White-Head Mountain", because the
summit area is never without some snow-ice-cover and the treeless crags there are grey-white,
while white is the most sacred color to Koreans; and "head" is fairly commonly used for the
Korean names of prominent peaks, such as "Yongdu-san" [Dragon's-head Mtn], there is a
sense of seniority or leadership implied.    白頭山 is pronounced in Chinese "Baitou-shan".  
North Korea's southern and eastern sector of the vast slopes and great lake (60%~40%,
depending on which source you consult), is now preserved and used for (mostly domestic)
tourism as the DPRK's "Baekdu-san National Park".

However, its contemporary name to the Chinese is Changbai-shan / 长白山 or 長白山 similarly
meaning "Always-White Mountain".  In the Manchu language it is "Golmin Shanggiyan Alin",
with the same meaning as in Chinese, "Perpetually-White Mountain".  Their northern and
western sector of the massive mountain (40%~60%, depending on which source you consult),
is now preserved and used for tourism as China's "Changbai-shan National Park".