Tunnel

This article is about the game mechanic. For the track in Bloons TD 5, see Tunnels.

For the track in Bloons Monkey City that is commonly referred to as "Tunnels" by fans, see Grass Terrain#Tunnels.

Tunnels, a map in BTD5 that prominently features tunnels

Tunnels are a game mechanic in the Bloons TD series, debuting in Bloons TD 5. They are sections of the track that shield Bloons from most attacks and from being targeted by towers.

Mechanics

Bloons TD 5 / Bloons TD Battles / Bloons Monkey City

In Bloons TD 5, Bloons TD Battles, and Bloons Monkey City, only regular Bloons can enter tunnels. MOAB-Class Bloons simply fly over tunnels, leaving them exposed. While inside a tunnel, Bloons are untargetable and cannot be hit by most projectiles, but will continue to take damage-over-time from sources such as Corrosive Glue and Burny Stuff. Bloons can still be hit by certain screen-wide attacks, namely the Glue Strike Ability, Absolute Zero Ability, Ground Zero Ability, and, in the Flash version only, Pop And Awe Ability, Super Monkey Storm, and Super Monkey Storm Pro.

Bloons TD 6

Bloons stop taking damage from dissolver glue while inside the tunnels on X Factor.

Tunnels are much rarer in Bloons TD 6, with only two maps having "true" tunnels as of version 36.2. Unlike in BTD5, tunnels shield Bloons from all sources of damage, including damage-over-time and screen-wide attacks. Additionally, MOAB-Class Bloons are able to pass through certain tunnels, with their models shrinking in order to fit inside and returning to normal upon exiting.

Bloons Adventure Time TD

In Bloons Adventure Time TD, MOAB-Class Bloons can enter all tunnels. Unlike in BTD6, Bloons will continue to take damage-over-time while inside them, like in BTD5.

List of maps with tunnels

Bloons TD 5

Monkey Lane Tubular (Deluxe only) Tunnels Skull Peak

Trick Or Treat Rabbit Holes Forgotten Garden Flooded Lane

Bloons TD Battles

• Bloontonium Mine
• Hydro Dam

Bloons Monkey City

Grass Terrain "Tunnels" "Pistol" "Yo-Yo"	Heavy Forest Terrain "Handcuffs" "Rose" "Coils"
Hills Terrain "Dip" "Seashell" "Subway" "Moustache"	Mountain Terrain "Treble Clef" "Monkey's Tail"
Snow Terrain "Checkerboard" "Pretzel" "Pickaxe"	Desert Terrain "Arrow"
Arid Grasslands Terrain "Slingshot"	Forgotten Garden (unused)

Bloons TD 6

• KartsNDarts (does not allow MOAB-Class Bloons)
• X Factor (allows MOAB-Class Bloons)

Additionally, some maps have structures that resemble tunnels, but are, in fact, composed of Line of Sight blockers, meaning towers that Ignore Line of Sight, such as the Alchemist, can still attack Bloons that are inside them. They are as follows:

• Logs
• Bazaar
• Spillway
• Dark Castle

Bloons Adventure Time TD

• Sinister Caves

Trivia

• Tubular and Forgotten Garden are the only maps in the Bloons TD series with see-through tunnels.
• While tunnels do not currently appear in Bloons TD Battles 2, the dinosaur spines on Dino Graveyard are blockers that resemble tunnels. Like in BTD6, they allow Bloons to be attacked by towers that ignore line-of-sight.