This is a list of 100 different hiding spots were valuable and important items can be hidden. Around a third of these hiding spots are suitable for any setting; the rest have a more modern twist. Some of the latter could date back as far as the eighteenth century, but the majority of the modern hiding spots will need the 20th century at the earliest, and especially the later end. The spots range in size from those suitable for hiding a single small gem or perhaps a microdot to ones that could be used to hide weapons. The hiding spots are predominately in buildings, but a few are for vehicles or people.
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Here is a sample result:
Painting - A canvas painting in a wooden frame. (The canvas of the painting itself has another layer of canvas behind it, providing a thin space for hiding such as documents.)
One page is the front cover and one page the front matter.