If you haven't had the opportunity to play any of the .hack games or view the multiple anime series, you are missing out on some of the most well composed anime and gaming music to come out of Japan. Do the names Yuki Kajiura and Chikayo Fukuda ring a bell? You should be nodding in agreement right about now if they do, and if they are new to you check out both composers disography! This particular song comes from the first .hack PS2 game, entitled .hack//INFECTION. For your audio delight-ness below is the Audire Soundtrack Choir version and the original in-game soundtrack.
"Hidden Forbidden Holy Ground" by Audire Soundtrack Choir
"Hidden Forbidden Holy Ground" by Chikayo Fukuda