Bloontonium Lab

The Bloontonium Lab is a track in Bloons Tower Defense 5 added on April 4th, 2012.

Overview
Not only is its difficulty extreme, but it is also considered the second hardest track in Bloons Tower Defense 5, the first being Tar Pits. This is the first track to be extreme difficulty, and few can beat it without Premiums or Special Agents. There are 3 entrances and 3 exits. The first entrance is on the middle-left corner, the second is on the top-right corner, and the last one is on the bottom-right corner. As for exits, the first is on the top-left corner, the second on the middle-right corner, and the last one is on the bottom-left corner. The player must have a Rank of 55 or higher to unlock and play it.

Like Main Street, which is also an extreme track, the player must be careful on how they play as there are high stakes. Each costs 50, so mistakes are very unforgiving. Also, there are no saves on this track and no Sandbox, Apopalypse or Deflation modes either. A successful attempt gives very high XP and many Awesome Points, with the rewards increasing with the difficulty.

Rewards
Easy: 100, 250,000 XP (500,000 for iOS), 900.

Medium: 250, 500,000 XP (1,000,000 for iOS), 1200.

Hard: 500, 1,000,000 XP (1,500,000 for iOS), 1800.

Note: Monkey Money rewards only apply to Bloons TD 5 Deluxe, while Awesome Point rewards only apply to the online version. The iOS version only gives XP.

Glitches

 * This track used to suffer from the Track Jump glitch.

Trivia

 * Just like all extreme difficulty maps, you can't play on Deflation mode, Apopalypse mode, or Sandbox mode. This is likely due to it being way more difficult to complete.
 * The difficulty doesn't apply to Sandbox Mode. Despite this, there isn't Sandbox Mode for this track. The same applies to Main Street and Tar Pits. This could be because it costs Monkey Money to play, or that they want the track to remain as hard as possible with minimal experimentation and attempts to find a strategy.
 * This is likely the place where Depleted Bloontonium Darts, Ground Zero bombs, The Big One Mortars, and the Technological Terror's plasma are made, hence the track's name and appearance.
 * The word bloontonium is derived from Plutonium, a radioactive metal.
 * This is arguably the hardest track in the entire BTD series, due to its multiple short paths, and the risks that the players are taking by trying to beat it. The other candidates for the hardest track are Monkeys vs Bloons, Triangle of Insanity, Down The Drain, Crypt Keeper (with Reverse Mode turned off), Tar Pits, Bloody Puddles and Workshop.
 * The Bloontonium Lab paths are apparently stained by tire tracks, similar to those on Drag Strip.
 * The circumference of the circle is similar to the track Clock. Also like Clock, the Bloons move towards the center and then away from it.
 * In Bloons Tower Defense 5 Deluxe, you get a lot of Monkey Money and XP for beating this & Main Street. However, you get more XP from this track.
 * With the short paths on this track, Ceramic Bloons can be very hard to beat, especially on rounds 43, 47, 49, 50, 51, 59, 63, 76 and 78. It's recommended to have an Arctic Wind tower in the center for those rounds, along with a 0/2+ Monkey Village or Tier 4 Ice Building for rounds with Camo Ceramics.
 * Even the rewards suggest that Bloontonium Lab is harder than Main Street, as the rewards are twice as much as they are for Main Street. In Bloons Tower Defense 5 Deluxe, this only applies to the XP gained.
 * The bottom path is the shortest path on the Track, in the same way the vertical track is the shortest on Main Street. This is probably due to the layout of the game, where the vertical length is shorter than the horizontal length.
 * Prior to the Tar Pits update, this track requires rank 60 or higher to play on Bloons Tower Defense 5 Flash.