Tunnels is an Expert track in which the bloons constantly enter tunnels, giving them temporary protection, bar M.O.A.B. Class Bloons, which will be visible moving over the tunnel.
- Dart Monkeys (4/2 upgrade) are considered effective in the track due to some straight lines seen on it and their cost efficiency.
- Glue Monkeys (2/2 upgrade) are extremely useful considering that the glue will continue popping the bloons through the tunnels. (2/3 upgrade) would be even more useful, as (2/2 upgrade) will not get all bloons.
- Ice Towers (in 4/2 or 2/4 upgrade) are useful in this track especially when the bloons reached the next tunnel.
- 4/1 or 4/2 Ninjas Monkeys are very effective on the straight parts.
- Keep in mind that this track is quite long although about half of it is covered; thus Spike Factories are quite essential for this track.
- Monkey Apprentices are highly useful on this track, especially upgraded to 2/2 or farther. The lightning can arc across multiple paths.
- A really useful strategy is to use 2/3 spike factories wove the tunnels; even though it seems like all the pikes aren't landing on the track, it damages MOAB-class bloons. The main problem with 2/3 spike factories is that spikes which could be used towards MOAB-class bloons will be used up by smaller bloons.
- It is possible to beat this map with just Dartling Guns and Juggernauts.
- Spamming 2/0 and 3/0 Engineers in Mobile along with a few 2/2 Spike Factories seems to work well.