Another map, proto_c17inner, from March 2001, also features this Citadel (the front and rear and reversed, compared to c17_04) and provides a closer look at the area behind the inner wall, featuring brutalist concrete structures and deep holes in the ground emitting greenish light. This version was to be separated from the rest of City 17 by a tall concrete barrier known as the "inner wall" or "inner gates". The Citadel is entirely brown and apparently not detailed, while a closer look shows it is detailed, featuring a round lump (seen in the posters), windows and other precise shapes. Prior versions of the map do not feature the Citadel, or even a 3D skybox, and in succeeding versions this variation was replaced by the next iteration. This 'rusty' version is featured in several revisions of the map c17_04, from revision 21 to 28, created from March to June 2001. The Citadel among American skyscrapers (Kirchmer). The vignette Old Friends from the uncorrected proof of Half-Life 2: Raising the Bar features a Citadel fitted with weaponry, making use of its supportive guy-wires to form an "Eye" which shot "spears of blazing plasma" at Gordon, Barney Calhoun and Isaac Kleiner as they attempted to escape City 17.Whether these versions made it past the concept art stage is unknown. Viktor Antonov, Dhabih Eng and Eric Kirchmer made several pieces of concept art depicting various iterations of the Citadel, including organic versions.3.2.5 proto_citadel_garbage / demo_citadel02.3.2.4 proto_citadel_cellblock / demo_citadel01.