The final museum I visited while in DC was the United States Holocaust Memorial Museum (USHMM). The Museum does an excellent job of approaching a difficult subject in a meaningful and respectful manner. The exhibitions are well contextualized and cover the Nazi rise to power, the final solution, response to the Holocaust, and contemporary forms of genocide.
This permanent exhibit halls are set up in a way which guides visitors though a very narrow hall and surrounds the visitors with images, video, and artifacts which speak to the atrocities of the Holocaust and the people impacted. I found that this layout had a very successful visual impact but also contributed to congestion at certain points in the exhibit -- as the halls were often too narrow to allow people to pass a group that was reflecting on a particular portion of the exhibit.
I think what shocked me most about the USHMM was the lack of formal health support readily available. Given the subject matter and the emotional impact of the exhibits, I would have thought health support would have been readily available at every turn in the museum. This is of particular note given the design of the permanent exhibit halls. Visitors begin at fourth floor of the museum and are directed downwards through the next two floors of the exhibit, creating a feeling almost of being corralled through the museum. There is not an easily apparent way for people who are experiencing distress to leave the exhibit hall without going through the rest of the exhibit.
Outside of the main exhibit hall, the Hall of Remembrance on the second floor of the USHMM does provide a safe reflective space for those interested in personal remembrance. The Children's Title Wall located on the lower level also provide a place for reflection and a more child friendly atmosphere for learning (the permanent exhibits are not recommended for anyone under the age of 11).
I was also very glad the museum has instituted a no photography policy for the exhibit halls. This policy helps maintain a sense of respect and remembrance while in the museum. I think not allowing photography also encourages a more reflective museum visit -- instead of focusing on taking photographs to share the experience with others. My visit to the USHMM was well worth it and inspired a lot of thought about the challenges surrounding the display of materials that can be emotionally and culturally sensitive.