The stairway in building A of Tuol Sleng – also known as S-21, or secret prison 21. Now a museum dedicated to the genocide in Cambodia, during the Khmer Rouge regime (1975 – 1979) between 17,000 – 20,000 people died here. Most were tortured in building A before being taken to the killing fields on the outskirts of the city to be executed. It was honestly one of the most difficult places – on every level, emotional, spiritual, physical – I have ever visited. But I was also determined not to look away.