One of the English papers had a story about the Japanese system of execution. The condemned is taken from his cell, allowed to pray at a statue of a goddess and led into the execution chamber. The chamber itself is an austere Japanese-style room with a trap door. You can see pictures of it here:
https://www.mirror.co.uk/news/world-news/death-penalty-execution-japan-hanging—10797256
Thanks! I watched the documentary a number of years ago and the prison would not let the execution chamber be shown. I don’t recall where the prison was located though. If I remember correctly the cells where the inmates where being held were even more bleak than the ones in the article.