This large, lush, walk-through aviary has zero barriers between the eagles and visitors, and the zoo was at one point considering replacing the bald eagles with Steller's sea eagles. Unfortunately there simply aren't that many available for zoos so that idea has been put on temporary hiatus.
This may be a quibble, but I wouldn't call it "walk-through" so much as "open front." You are never really in with the eagles. Woodland Park Zoo has other true (and terrific) walk-through aviaries.