I've just learned within the last few days that ABC is planning to tear down the remaining Lost sets in Oahu, including the Jughead structure, the Orchid Station, the Temple, and the Hydra Island cages. This would be a terrible loss not just for Lost fans but for Oahu tourism as well. Hopefully ABC can be convinced otherwise.
The Hydra Island cages are located just a few steps away from the Orchid Station in Pleasant Park. My understanding is that the buildings and walkways near the cages were already in place but the two main cages were built by the Lost crew.
The next two screencaps show the location as it appeared early in season three, followed by its appearance in season 6.
Again two similar screencaps, the first from season 3 and the second from season 6 after Widmore's people had set up shop.
The Hydra Station emblem was just barely visible on the walkway canopy during our visit; in fact it wasn't until our guide explicitly pointed it out that we noticed it at all.
As with the Orchid, the cages have seen better days. However, the Orchid set we visited had always been shown on-screen in a dilapidated state so the additional decay wasn't overly jarring. The state of the cages was a bit more shocking, particulary considering that they must have been touched up in early 2010 to shoot the scenes with Widmore's team.
I seem to be in the minority, but I really love the cage scenes during the early part of season 3. The whole bit with Sawyer puzzling out the water and biscuit reward system was very entertaining. That mechanism has been removed, but one can still see the troughs into which the water flowed.
Although Sawyer is its most frequent resident, Jack also spent time in the larger of the two cages following his intentionally botched surgery on Ben's tumor.
Kate's cage is in even worse shape, with only two partial walls left standing.
Alas, Kate's cage-climbing days would seem to be over.
Is it just me, or did Kate never look lovelier than she did sans makeup in a dirty sundress sitting somberly in her cage?
For your consideration ... we all sat in hushed reverent silence as @kiwilostie re-enacted Kate's cage scenes.
However, I had a somewhat negative reaction when he asked me to help recreate the scene from I Do -- you know the one.
There are several covered walkways in the area. Some make appearances in a few season 3 episodes.