The Old Idaho Penitentiary operated from 1872 until 1973, a century during which it housed outlaws, murderers, and the occasional political prisoner in its sandstone cell blocks. The inmates quarried much of the stone themselves from the nearby Table Rock mesa — a bleak but efficient arrangement that suited frontier-era prison economics.
Today the site is a state historic site offering self-guided and guided tours through the cell blocks, solitary confinement, the gallows, and the rose garden planted by inmates in a futile attempt at normalcy. The history is grim and the building is genuinely atmospheric — flickering lights have been reported in the women's prison section, which is reliably the most popular part of the tour. Located about 3 km east of downtown, it is worth the short drive.