At first glance and without knowing the complex's history, the upper-most photo of this Photo Hunt entry may seem somewhat innocuous and not have much about it that is undesirable. After all, the pictured place seems to be in a nicely quiet section of Seoul and the solid constructions in it that could be -- and were -- filled with hundreds of people at a time look like they may have been factory buildings dating back to the early 20th century.
But a tour of that which now is a museum shows that Seodaemun was built in 1908, at a time when Korea was under Japanese rule, as a prison and served as such through the period of Japanese colonialisation (to house captured Korean freedom fighters and other patriots, male and female -- something that is emphasized in the official literature) but also after through to 1987 (something that it much less noted by the official history of Seodaemun Prison).
If one were to read the linked pieces above, one will learn about a lot of undesirable activities taking place at Seodaemun Prison (and also with regards to the way its history is presented). And while the people incarcerated at this complex were seen as undesirables by the ruling powers of the day, the strong feeling I get after reading what I've read about the place as well as visiting it is that the more undesirable elements of society actually were those who often unjustly condemned women as well as men to miserable fates within the prison's walls and those officials who carried out some incredibly awful tortures and related acts in the name of the then prevailing law.
And for those who think this is all too abstract, look at the middle and bottom photos in this entry and realise that: the former gives one a look right into the dark tunnel officially known as the Corpse Removal Exit -- located next to the execution building and used to secretly remove bodies to the public cemetery outside the prison to conceal the existence and number of executions that took place at Seodaemun; while the latter is of underground solitary cells specially constructed to house some of Seodaemun's female prisoners and in such a way that part of the terrible torture treatment they received there was that they never could get any natural sun light -- and also in the case of the taller ones, could never stand up straight -- in them.