There is more than one artist with this name: 1) Citadel is a power metal band from St. Petersburg that started in 2001. They got one EP "Citadel" (2003) and album "Игра Света и Тени" (2008) . http://www.citadel.su/
http://www.myspace.com/citadelspb 2) Citadel® or Citadel ® is a prog rock band from the USA. http://www.citadelband.com still together after almost 30 years and 10 albums, also co-founders of Progfest in LA, which started a prog rock rebirth in 1993. 3) Citadel is a local band from petaluma. they broke up early 2006 but their music still lives on.

Read more about Citadel on Last.fm.