While i was on holiday in London recently, i visited the Imperial War Museum. It was a realistic window into our modern history.
I found the Holocaust Exhibition to be the most interesting and moving. Starting with the rise of the Nazi Party the exhibition tells the story of the mass extermination of a race of people. Personal letters and photos were among artifacts from the extermination camps.
If you live near London or will be visting soon,then take the time to visit this Museum, entry is free.