Inverted Volcano is the fourth stage in Gradius. The level is Gradius Arcade Stage 1, Volcano Stage, upside-down (hence the name "Inverted Volcano"). Eventually, the player will reach the area in which the Vic Viper originally endured the Volcano, but instead, Iron Maiden replace the former as a Sub Boss of the level. In the NES version, though, the Volcanoes reprise their role as Sub Bosses. After defeating Iron Maiden, Big Core will appear as the boss, as usual.