Halla-san, the Great Mountain
Halla-san on a rare clear day, August 2003, from the southeast.  At 1950 meters, it's the highest
peak in South Korea.  A huge ancient volcano which formed this entire island, it has been dormant
since 1007 CE.   I found 14 Buddhist temples and one mountain-shrine on its ample well-forested
lower slopes (there are none up in the alpine areas, which are protected as a National Park).
The crater at the peak is named Baek-rok-dam or Baengnok-dam
[White Deer Pond] and is the holiest site on Jeju-do.  There is a
small lake in it which changes size according to the weather.
White animals such as deer, cows or tigers (albinos?) are
considered sacred by Koreans.  An old tale claimed that 100
Shin-seon [spiritual-immortals, enlightened persons] enjoyed
riding around on white deer up here, hence the name.  Annual
ceremonies to Heaven and the Spirit of Halla-san were held here
until the 15th Century, when the altar was moved to the NE slope.
 More on the importance of this crater is
here.
The dramatic rock formations on the
south-western slope, starting from the
Yeong-shil [Spirit-room] trailhead and
marching upwards to the peak, are
known as "the Five Hundred Disciples
of Buddha"
(see these pages for more on
the common-in-Korea religious concept of
outstanding rocks as manifesting Buddhas).
2008 newspaper shot of Royal Azalea flowers on Halla's slopes with the cone-peak in the background
Halla-san's several lava-tube caves have always been part of why it's regarded as an especially sacred mountain
to Korean Shamanism.  In 2007 they were added to UNESCO's listing of World Natural Heritage Sites, along
with the volcanic cones Baekrok-dam and Ilchul-bong.  Upper Left is the entranceway of
Manjang-gul [10,000
Guardians Cave], Upper-Right is the "Millennium Lake" in
Yongcheon-gul [Dragon-Stream Cave], and Below is
a man meditating amongst the carbonite stalagtite/stalagmite formations of
Dangcheomul Cave.
Robert Neff writes a lot of fascinating articles about Westerner's encounters with or residency in Korea a
hundred and more years ago.  This article "
The First Westerner to Climb Mt. Hallla", about "well-educated
German journalist" and "adventure-seeker" Siegfried Genthe, in The Jeju Weekly gives wonderful details on
how some of the Sanshin Mountain-spirit beliefs were functioning in regard to Halla-san way back then:

"The governor, wearing yellow silk and red shoes, presented Genthe with wine and then made a rambling
speech before he got to the point – “You may at no price climb Mount Halla.”

The governor then went on to explain that “never has anybody been on the summit, neither native nor stranger.  
The mountain spirits would surely plague the island with bad weather, thunderstorms, poor harvest and
pestilence if anyone were to approach them and disturb their rest.  A bad harvest would cause the people to
blame you, the foreigner, and no doubt would result in your physical harm.”

But the governor wasn’t quite telling the truth. When Charles Chaillé-Long visited Jeju in 1888 he was
basically told the same thing except that the governor noted:

"One hundred days of sacrifices must be performed in any case before attempting to climb
the mountain in order to propitiate the spirits of Halla-San.” If the sacrifices were not made
or the mountain was defiled, “the people and the island and the crops would be certainly
ruined by the rains which would surely follow.”

Just as Governor Yi finished warning Genthe that he must not climb Mount Halla, a horrendous thunderstorm
struck the city.  The roaring winds and the pounding rain were too much for the governor who fled back to his
residence convinced that the mountain spirits had spoken – no one was to climb the mountain."
The Sanshin spirit of Halla-san was indigenously
conceived-of as a matriarchal ancestral-of-all
goddess named
Seolmundae, with the 368
oreum volcanic-cones as her daughters, much
like the traditions of
Jiri-san Cheonwang-bong
Seongmo-halmae Sanshin.  This slowly changed
towards Concucian male-spirit concepts with the
imposition of mainland culture, especially after
1948, but not very thoroughly; the original female
depictions are now being widely revived.    See
Anne Hilty's article in the Jeju Weekly for more
info and some good sources.