Park, wearing a traditional Hanbok robe, and other participants unveiled a large wooden tablet bearing the gate's name.
They then swung open its studded wooden door watched by guards wearing traditional clothes and carrying swords, spears, and bows and arrows.
The restoration project - one of the longest and most expensive ever undertaken in South Korea - involved more than 1000 craftsmen who used traditional tools to restore the gate to its former splendour.
All 22,000 roof tiles were made by hand. Raw materials for decorative paints had to be imported from Japan, since Korean specialists had lost the art of making them in the traditional fashion.
Fortress walls that were destroyed during Japan's 1910-45 colonial rule were returned to their original form.
The largely wooden structure - which survived the devastation of the 1950-53 Korean War - was almost reduced to ashes by a disgruntled 69-year-old man with some paint thinner and a cigarette lighter on 10 February 2008.
He torched the gate after claiming he had received insufficient compensation following the expropriation of his land as part of an apartment-building project in Seoul's northwestern satellite city of Koyang.
Its destruction in 2008 sent shock waves through the country, with sorrowful citizens swarming around the charred ruins, laying flowers and writing grieving messages.
The arsonist was eventually sentenced to 10 years in prison.
- AAP