So as we know that the Kedarnath Temple was redeveloped in 8th Century, which makes it almost 1200 years old. But it was re-developed back then. The Origin of the temple is way more older that that, maybe more than 5000 years.
It is said that the Pandavas, who were the winners of Mahabharat war, where they had to kill their brothers, relatives & brahmins, wanted to seek forgiveness for these killings from Mahadev Shiv. And hence they went to Kashi, which is the city of Mahadev. But Shivji was in no mood of seeing the Pandavas and thus he disappeared from Kashi.
Later Pandavs were able to find Mahadev, who has taken the form of a bull & was roaming in Garwal region of Himalayas. Pandavs went there but couldn’t find Mahadev as there were so many bulls, making it impossible to find Mahadev.
So the Pandavs sought out a plan where Bhim, the 2nd Pandav increased his body size (a vardan which he had) and stretched his legs, which also created the valley where Kedatnath Temple and all dharamshalas are situated.
The Pandavas then forced all the the bulls to pass under Bhim’s legs and then it was Bhim who noticed that one particular bull is not coming to him, and he realized that this bull must be Mahadev himself.
So Bhim grabbed that bull from back and as soon as he did, the bull disappeared.
Origin of Kedarnath Temple
When the bull disappeared, all 5 body parts of the bull came out of the ground like the Hemp of the Bull come out in Kedarnath area, and it is said that the Kedarnath temple was built around that Hemp.
Similarly the arms of the bulls appeared near Chopta where Tungnath Temple is created, the face of the bull appeared in Rudra Nath where Rudranath Temple was created, the navel & the stomach appeared in Gaundar & Urgam Valley which led to the creation of Madhyamaheshwar and Kalpeshwar Temple.
And all these 5 temples are also known as Panch Kedar. The Yatra of Panch Kedar is more difficult then Char Dham, and only Kedarnath Temple is a part of Char Dham Yatra, one of 12 Jyotirlinga and 275 paadal petra sthalams.
Today the Kedarnath Temple is situated in Kedarnath Valley which is at a glacier, and next to Mandakini river. The first sight of the valley where the temple is, is so beautiful that all the travelers who started Kedarnath Yatra from Gaurikund simple forget their 18-20 km trek and just get lost in the atmosphere.