The Auschwitz-Birkenau Memorial and Museum has created three online virtual tours of the Auschwitz-I and Auschwitz-II-Birkenau death camps. On these sites the Nazis built the largest of its concentration and extermination centers. Over 1-million people (men, women, and children) were killed there.
Clicking on any one of the tours takes you to a panoramic bird's-eye view of the site today. You can then pan left-right, move up-down, and zoom in-out as you "tour" the site. A short, very helpful guide explains what happened at each site, along with links to additional very-accessible background information.
T/H to @AuschwitzMuseum for this link.