I read from one of the posts in Skills and Classes Section about Pagan's Temple, a place where high level Bishops can own. Since they said it is in Rune and I cant find it in the map, I researched about it. Just like my speculation, it is the place below the Einhasad Temple in Rune. But in order to access the place, you must be able to do the "The Truth Beyond the Gates" quest [Lvl 73] in Rune.
http://l2vault.ign.com/View.php?view=Guides.Detail&id=351
http://www.lineage2media.com/pagantempletruthbeyondthegate.html

And another quest "The Truth Beyond the Gates Once More"
http://www.lineage2media.com/pagantemplethroughthegateoncemore.html

The first one just teleports you while the second one allows you to open the doors to Pagan's Temple.

You don't need to make the 2'nd quest for Pagan's Mark to be able to open the doors from Pagan.
Another way to open them is to use the npc gk behind the doors . /target him (temple gatekeeper or somethink) and tell him to open the doors from inside.
So you need only Visitor's Mark (5minutes job) from 1'st quest.
And yes , to do this quest you need 73+.. that doesn't means only carachters who are 73+ can enter , because there's always a summoner/gate chanter inside Pagan.

Pagan's onwz in Exp. But there's lies a big problem. SP.

Is much lower.