Urchin Underpass

Urchin Underpass is a multiplayer stage in Splatoon. It is also used in Octo Valley mission #21, Unwelcome Flying Object, as well as the Battle Dojo in the old version of it.

Layout
Urchin Underpass consists of two large L-shaped areas of land that are joined together by a rectangular piece of land between them. A large, open area in the center of the map. This area includes railings, ramps, grated platforms, and two trees. On either side of the map are two passages that extend from the teams' bases to the Center Plaza. These passages act as alternate routes to get into the middle of the map, as both alleys have two exits that lead into the Center Plaza. Much of the floor is un-inkable glass. At the end of either teams' bases are a set of multi-level ramps that lead from the base into the Center Plaza. The layout of these ramps allows for multiple exit options, making bottlenecking a challenge.

Splat Zones
The Splat Zone in Urchin Underpass is located at the very center of the map. It is the smallest singular Splat Zone in Splatoon so gaining and staying in control requires lots of attention to it. Boxes have been added near both ends of the Splat Zone to provide protection from enemy fire and a vantage point to attack the Splat Zone.

Tower Control
In Tower Control, the tower starts in the Center Plaza. It moves straight back towards the enemy territory and climbs up. Then, it moves to the rider's left, climbs back down, and reaches the goal.

Rainmaker
The Rainmaker in Urchin Underpass is located in the center of the map, just below the two ramps in the center. The goal is at the end of the small strip of land with 4 stripes in front of the opposing team's base. Two stacks of blocks have been added to help both teams get to the center of the map faster.

Splatoon
Urchin Underpass underwent a series of changes between its development period and release.

Pre-release version
Pre-release Version of the center of Urchin Underpass with a rabbit that was chosen as the design for the characters. Very similar to the E3 version and the release version of Urchin Underpass.

E3 version
The pre-release version included many differences, such as:
 * A water tank guarded by a fence could be found in the corner of teams' bases.
 * The raised platform opposite the Spawn Points in teams' bases was accessed by one smaller ramp, included a wooden plank used to swim up through a grated platform, and did not provide access to the Center Plaza.
 * The lowest area in teams' bases was much larger.
 * When leaving a team's Spawn Point and heading left, the first ramp encountered was not present. Instead, players could go around the raised portion on either side. This raised portion was split into three differently-sized platforms, and a window was not present in this location.
 * The walls of the Secret Alleys were concrete, not glass.
 * When entering the Center Plaza from the main entrance, a small fence acting as a grated barrier was present on players' immediate left.
 * The ramped platforms allowing players to jump to the other side of the Center Plaza were directly opposite each other.
 * The middle area in the Center Plaza was slightly smaller.
 * The grated walkways outside the Secret Alleys in the Center Plaza were extended.

Release version (Prior 1.3.0)
In this version, the center of the is almost the same as in the E3 version but each side's base was changed completely from removing grates and high platforms to ramps and high advantage points. There are two alleys located near the Center Plaza. They are long, narrow, hidden-away strips of turf that are difficult to access which have two Glass panels. This version was not balanced and Nintendo decided to make some changes so it will be easier for both sides to play on it.

August 2017 Update version (Latter 1.3.0)
On July 27th, 2015, the official Splatoon Tumblr announced that Urchin Underpass would be undergoing maintenance between August 2nd and 5th. They released an image showing the original map scribbled on, allowing fans to see what about the stage would be changed. Many features were altered, including:
 * The trees near each team's base were moved to the center of the stage.
 * The secret alleys were extended and pushed further away from the central area. They were also widened, and given another access point to the center area.
 * The grated walkways protruding from the secret alleys were removed.
 * The ramps leading into the central area were made so that they only took up half of the available space. The other half became flat turf.

Trivia

 * An early version of this stage was first revealed at E3 2014 and was the only playable map at the time.
 * Urchin Underpass is the only map in Splatoon that has been changed almost completely after being released.
 * Near the center area is an inaccessible, L-shaped space, which can be seen by standing on the vending machine in the corner. The floor and walls are fully textured to match the rest of the stage, but the floor is not solid; Sub Weapons thrown in will never be heard landing.
 * The utility poles featured in the teams' bases are decorated with various license plates, many adorned with the Splash Mob and Forge logos. It is unknown what purpose these license plates serve.
 * Before Version 2.0.0, two utility poles in the center of the stage featured the same license plates, but with Shrimp Kicks and Krak-On advertising instead. They were removed in the update.
 * Its design and Japanese name are based on Jūjō-dōri (十条通, lit. Tenth Road) in Kyoto, near which Nintendo's headquarters is located.
 * There is a battle course named Urchin Underpass, similar to its Splatoon version, in Mario Kart 8 Deluxe for the Nintendo Switch.

Names in other languages
Passage Turbot