While most people will say Keys to the Kingdom, we actually found of the tours we have done, that one showed the least behind the scenes. It was almost more of a history lesson with a few trips backstage, but we LOVED our guide (Mathew!), so we weren’t too bothered by not seeing much behind the scenes or going on rides. We did the Backstage Safari at AK, which became Backstage Tales, which probably showed the most behind the scenes (almost all the tour was backstage, showing the different animal housing areas, the kitchen, etc.), but now I don’t even see it on the Disney website (it would be a shame if they stopped this one). UnDISCovered Future World also showed a lot behind the scenes (I think the only time we were actually on stage was when we cut from where we met to The Seas pavilion and then when we cut from the land pavilion to the VIP room in Mission:Space). We went through places like costuming where we saw Snow White getting her makeup ready and heard about that whole process from her and the garage for the cars of Test Track (amongst others). So based on the ones we did, I would recommend Backstage Tales if it is still offered, UnDISCovered Future World and then KTTK. Behind the Seeds was also nice, and while it is a tour I don’t count it with the tours since you don’t really have to plan ahead to book it if you don’t want to (but you can if you know when you want to take it).