Exhibition Palace at the Great Exhibition (or the first Worlds Fair) in London in 1854.
More images here.
The Worlds Fairs served as the 19th century's largest gatherings producing perhaps the largest crowds in the entirety of the history that proceeded them. They provided the need for security and a "watchful gaze" that was unprecedented.
Similarities between the Panopticon and the Crystal Palace:
- Both tools for surveillance (one explicitly, the other as an inherent design feature)
- Both architectural tools
- To a degree, both present a situation where is visible (or in the case of the Crystal Palace, at least assumed) and unverifiable