Downstream is an Intermediate Map introduced in the Version 4.0 update on 12th September 2018.
The track consists of a river alongside a looped stone path crossing said river a number of times. Bloons start from the top, loop around twice, and then exit towards the right of the screen, following the stone path.
The two rock piles within the circles can be removed for $350 each. They do not block Line of Sight limits, but they do prevent towers from being placed on them until they are removed. The rocks present on the banks of the river are NOT removable and do not allow towers to be placed on top of them.
- Both of the circles allow towers with circular damage to be very effective, some being the newly-buffed Glaive Lord, Super Brittle, and Inferno Ring.
- The water surrounding the first river crossing can be very powerful positions for Destroyers or any straight-firing towers on Pontoons.
- This track is the first map in BTD6 to be added in an update that does not add a new hero.
- This track is the first map to be named after an already existing map name without being related to the original map at all.
- The trees closest to the entrance allow snipers and other smaller towers to be placed under them.
- The track bears a resemblance to River Terrain tracks in Bloons Monkey City.