Balloon 1 (Shipyard, Dry Dock)
After using the big red button to open the first gate, head on through. Before descending the stairs ahead, look up and to the left.
Balloon 2 (Shipyard, Access Corridor A)
Just after taking out the second trio of thugs, you’ll come upon a huge locked door marked “Warehouse.” Look for a balloon just above this door.
Balloon 3 (Shipyard, Access Corridor A)
After your first proper usage of explosive gel, continue on until you reach a small pool of water. Walk to the edge, turn around, and look above the door.
Balloon 4 (Shipyard, Pump Room)
You’ll find this balloon attached to a chair, just to the right of the first sniper’s position.
Balloon 5 (Shipyard, Pump Room)
From balloon 4, turn around and head up the stairs. Look above the caged area to the left of the three thugs working on the door.
Balloon 6 (Shipyard, Pump Room)
After popping balloon 4 and 5, proceed in the intended direction, which is through the double doors with the word “Warehouse” above them. Run straight ahead and you’ll spot a balloon across the long pool of water. Use your shuriken to pop it.
Balloon 7 (Industrial District)
As soon as you have control of Batman, look up above Commissioner Gordon’s head. There’s a balloon on the left bridge support column.
Balloon 8 (Industrial District)
It's on the easternmost brick smokestack, along with a few birds.
Balloon 9 (Industrial District)
It's on top of the Ferris wheel.
Balloon 10 (Industrial District)
There’s a building with a large “Sionis Industries” sign on the roof. A balloon is just behind this sign, attached to some loudspeakers.
Balloon 11 (Industrial District)
From street level, find the green “Joker’s Funland” sign above an entrance blocked by a van. The statue to the left of this entrance holds a balloon.
Balloon 12 (Industrial District)
Just southwest of the crane, there’s a small tower with a sniper. There’s a balloon attached to the corner of this tower’s railing.
Balloon 13 (Industrial District)
At the base of the tower with the “Tricorner Naval” sign, you’ll notice a nutcracker statue. The balloon is tied to that statue’s hat.
Balloon 14 (Industrial District)
West of the Steel Mill, there’s an alley where you’ll find the torso of a nutcracker statue with the head of a Harley Balloon.
Balloon 15 (Industrial District)
South of the Steel Mill, at street level, look for the gate with two Harley statues on either side and the words “Burn in Hell” draped across it. The balloon is on the other side of that gate, just to the right.