The primary religions in Korea are Christianity and Buddhism.
Despite it's late arrival in Korea, Christianity is the primary religion of about 21 percent of the total population. Christian churches and cathedrals are common throughout the land. South Korea has the second highest rate of Christianity in eastern Asia, with the Philippines being first. Christianity in Korea is usually associated with modern reformist thinkers.
Buddhism, not surprisingly, comes in a close second in Korean religion with about 20 percent of the population. Buddhist temples are typically beautiful, secluded compounds high in the mountains, though a few are located within the cities. Buddhism is Korea is typically associated with conservative, old fashioned thinking.
Although Buddhism is still the dominant religion in South Korea, there is the emergence of Christians especially among the younger generation. As such, you will find more and more churches in Seoul with time, like the one shown in the photos taken by me in November 2008.
If you are in Korea in early May, make sure you join in the celebrations for Buddha's birthday. There are parades spread out over three days, paper lanterns everywhere and on one Sunday they closed off a street in Insadong for a variety of tents demonstrating Buddhist practices. There was a tent where you could get a leg massage and another where you could have small candles burnt on your hands to purify your body. They even had a tent titled "Try North Korean Food" -- ironically the table tops were empty! It's pretty clear that no one involved even cares if you are Buddhist, as one tent had a lantern-making contest for foreigners.
Jangseung are wooden totem poles or spirit sentinels that were placed at the entrance to villages to guard against evil spirits, natural disasters and military invasions. You can see them in the grounds of the National Folk Museum in Seoul. Shamanism is still actively practised in Seoul.
Later jangseung were made of stone. This one also stands in the grounds of the National Folk Museum.
The swastika sign has always meant temple in Asia. The Nazis appropriated it and reversed it, making it a universal symbol of evil in the West.
in seoul, i find many churchs on the street, different style and size. they are quiet and nice, make me very comfortable.