|This location exists primarily or exclusively within the Sonic Boom continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
The Fissure Tunnels are levels that appear in Sonic Boom: Fire & Ice. They are a series of bonus levels that the player can enter from the World Map. Here, Sonic the Hedgehog races through an elemental tunnel overflowing with fire and ice elements to the wellspring of a giant fissure.
Fissure Tunnels are underground tunnels with stalactites and fissures at the end which switch between two environments: one is red-hot with magma floors and thin magma falls, while the other is ice-blue with ice crystal clusters. Along these tunnels are sections of paths made of harden magma or ice. These paths are aligned next to each other so they outline a tube or half-pipe. At various points, there are mechanical gates that open as Sonic approaches. On the World Map, the Fissure Tunnels look like giant fissures.
In a Fissure Tunnel, the player plays in 3D, unlike the 2.5D adventure levels. Here, Sonic is stuck at full run and can only move left and right (akin to the Quick Step). While running, Sonic's position in the tunnel is shown on the bottom screen of the Nintendo 3DS. The Fissure Tunnels' gimmicks include Bounce Pads and Ener-Rails which are used to cross chasms or reach otherwise inaccessible rails. There are as well Boost Pads and Dragon Rings, the latter of which will reward Rings if completed. The player can also press and hold down to boost Sonic's speed.
Along the path, there are obstacles that require Fire/Ice Mode, both of which the game will tell when to use. These include ice blockades which must be melted and gusting water which must be frozen to make bridges over gabs. Other obstacles also include green and red energy circuits and elemental pillars. Touch or fail to counter any of these obstacles, and the player is forced to restart the level.
An area's Fissure Tunnel becomes available after clearing the first levels in said area. The general goal of all Fissure Tunnels are the same: Sonic races down a pre-set path and it is the player's objective to guide him safely to the end of the tunnel. During the course, the player must shift lanes to dodge obstacles, use gimmicks and initiate Fire/Ice Mode to move between sections at the right time. The player can also collect Rings to obtain extra Ragnium.
The Fissure Tunnel get progressively harder as the player advances with the game, with obstacles appearing more frequently and the time to react decreasing. Upon clearing a Fissure Tunnel, Sonic finds the local fissure and seals it, marking the end of the level.