"The most moving day of filming, where we all felt history in the most intense way, was in a room in the Catherine Palace in St. Petersburg. It was a large gallery above her private bathroom, and had never been filmed in before. Towards the end of the series, Catherine receives a letter with some bad news, walks into that room, and falls to the floor. That floor is the very same wooden floor that Catherine herself lived and walked on. It hasn't been changed. It was very worn, and had these incredible scorch marks from where the Nazis made a fire and cooked food when they took it over."