We did the Motown Museum last year. It was absolutely awesome (for a Motown nut like me anyhow). The nice thing is that the recording studio, sound room and techy stuff if pretty much still intact. Original wood floor, wall panelling etc. The smell of the place is unique as well. All those years of smoking various stuff, sweat and everything else that went into the melting pot. The other thing that is no immediately obvious until you go there is the size of the studio, it's actually quite small and how they crammed all of the artistes into there for a session and mic'd it all up must have been an art in itself. The early recordings were made on a three track recorder if I'm not mistaken. During Motown's time in Detroit Berry Gordy had taken over half of the street as quite a few of the surrounding houses were used for marketing, advertising and the school of etiquette. All of these buildings have now been sold on.
Unfortunately, apart from the Museum there is not too much left in Detroit relating to the Motown years. The 20 Grand Club had been demolished some years ago. One minor disappointment for me was that they don't allow cameras to be used in the building, but that seems to be the norm for most of the exhibitions over there.
Molan, if you are planning to get over there make sure you put Memphis on your list of places to visit. It's a muso's paradise. You've got Stax, Sun Studios, Gibson factory, Gracelands, Beale Street, BB Kings, the list is endless.