The sandstone that formed the prison's walls was a plentiful and inexpensive building material, but
is also intensified the temperatures inside the cells. In the hot Boise summers, the sandstone
retained the heat, creating a stifling oven effect; in winter, the walls held the bitter cold,
chilling the prisoners for months.

About a year after the prison was placed on the National Register of Historic Places, it opened up
for tours. Guides and visitors attest to the sinister feelings, strange sounds, voices and the dark
entities they feel are still lurking in the cellblocks of Old Idaho State Penitentiary. All of the
eerie activity intensifies near the frightening solitary confinement cell (dubbed "Siberia" by the
inmates) and the gallows.