It's difficult to imagine visiting Amsterdam and not visiting the Anne Frank House. We were grateful that our classmate had organized ordering tickets online a couple of months before because entrance is strictly limited to online purchase and those tickets sell quickly.
The tour is self-guided with the aid of a listening device. The non-secret parts of the house have been filled with interpretive exhibits to give a sense of the era, the people, the political climate, and the Frank family's experience. The 2nd and 3rd floors of the secret annex are bleak--largely left the way they were found after emptied of valuables by the Nazis, per Otto's request.
Visit, contemplate, and prevent this sort of thing from happening again.
(Also, please resist the urge to snap peace-sign-flashing selfies at memorials such as this.)