Today I visited the Museo de la Memoria y los Derechos Humanos. Here is the outside of it. Unfortunately they do not allow photographs on the inside.
It is a very powerful museum. As you walk up the stairs, you see images of the coup and speakers pour out the sound of soldiers yelling. There are then a number of screens with headphones, so you can see and hear the declarations of the junta, Salvador Allende's last broadcast, and a variety of videos of the air force bombing La Moneda. All of those are unedited and so are just simply presented for you to contemplate.
As a father of young children, the most emotional part for me was seeing the letters that children wrote to their imprisoned parents, which sometimes included drawings of the family.
Obviously human rights is a political issue, but the museum is not politicized. Instead, it focuses on the idea that human beings deserve certain rights, and so focuses on who denied those rights and who fought to protect them.
The placed was filled with school children, and the long-term hope is that this sticks with them when future political crises hit. It creates a living memory rather than something you just read about. Chile has had many conflicts, and often they were resolved with amnesties that served to sweep things under the rug (on this point see Brian Loveman and Elizabeth's Lira series of books on amnesties in Chilean history).
If you get to Santiago then you should not miss it.