https://phys.org/news/2018-11-deliberately-prison-iceland-didnt-cell.html

Iceland's open prisons are simply very open. The absence of security features was striking. The first prison I stayed in, Kvíabryggja prison in the west of the country, had little in the way of perimeter security. There is, however, a sign instructing passers by to keep out – mainly aimed at tourists.

I could simply drive up to the small, mostly single-storey building and park up. I then walked in (yes, the doors were open) and said hello. And I was immediately made a dinner by one of the prisoners, who recognised me from a previous visit. I spent the week experiencing daily life as a prisoner.