The Botanical Gardens in Arkham East.
The Botanical Gardens of Arkham Asylum provided fresh greenery as possible rehabilitation for the institution's inmates. It included a Statue Corridor, an Aviary, and even a top secret Titan Production Facility that was used by Dr. Penelope Young.
With Arkham East the only part of Arkham Island under control during the early stages of the Joker's takeover, security guards were posted around and within the Botanical Gardens.
While several guards patrolled the outside, one guard was posted at the Glasshouse Entrance, and two others at the entryway to the inner Botanical Gardens. Shortly after armed convicts stormed Arkham East, the gardens fell to them as well. Victor Zsasz raided the Glasshouse Entrance, killed the security guards, and arranged them in lifelike poses around a bench. The Joker's men then entered the inner Gardens, and met little resistance.
After Batman defeated them, he continued back through the Abandoned Corridor, and to the other side of the Flooded Corridor, where two convicts had turned the power back on, and attempted to trap him on the other side of the Flooded Corridor by re-electrifying the water. Batman grappled across the water by using his Line Launcher and defeated the Blackgate Prisoners. Batman returned to the Glasshouse Entrance after he defeated five more of the Joker's men in the Botanical Glasshouse. Here, the Joker broadcast triumphantly over Arkham's intercom that he had supplied Poison Ivy with Titan.
The plants of the Botanical Gardens mutated, overran the Gardens, and mainly destroyed the Garden's facilities. Batman found his exit blocked by the mutant plants, but escaped by using an alternate route through the flooring. The remains of the Botanical Gardens soon became filled with Titan Pods which could spit toxic gas orbs at any movement. Batman returned to the Gardens to battle Ivy, who cleared her vegetation out of the way for him to proceed. Ivy allowed Batman to re-enter the Flooded Corridor, where she unleashed two security guards under her control to attack and weaken him. After being forced to defeat the zombified guards, Batman was lured further into the Gardens by the mutated plants.
Batman found Ivy in the Elizabeth Arkham Glasshouse, where she bounded with a Titan plant, and controlled the massive plant from inside its mouth from behind a protective shell. Ivy powered toxic vines to grow out of the ground and sent the Arkham security guards that were infected by her mind-controlling spores after Batman, who finally knocked down all the guards, fought off the vines, detonated Explosive Gel on the mutated plant and defeated Ivy. The ruined Botanical Gardens were reclaimed by the GCPD as they recaptured Arkham Island after the Joker's defeat.
Rooms
Glasshouse Entrance
Botanical Glasshouse
Flooded Corridor
Statue Corridor
Glasshouse Generator Room
Abandoned Chamber
Aviary
Titan Production Facility
A factory is hidden behind a wall in the Aviary. Inside are venom plants that produce Joker's Titan formula, with many of them contained in six canisters. Batman destroys the containers to put an end to Joker's scheme.
Elizabeth Arkham Glasshouse
Poison Ivy took refuge here as the path to the Glasshouse was destroyed. The room is later completely destroyed when she loses control of her plants.