So, I've had this idea quite a while and figured now was the time to put it out there since technology is always improving.

Since the World's Fair played such a huge role in our history, I figured why not push for a VR thing that people can download to their phones or whatever and then walk around Forest Park and see how the World's Fair was. I don't know how much this would cost nor what it would take, but think about it. VR has the possibility of being a true time machine for people. With the way graphics are getting and other things, I imagine you could get some headset, or use your phone as an AR thing, and walk around Forest Park looking at how it was during the Fair.

I think people would like this as it would be an interactive history thing. There would be people you could interact with who would tell you the story of the Fair. Other options would include a time-lapse of the construction of the Fair from a certain vantage point or using the phone's camera as a way to take a picture of yourself, or friends and family, on the Fairgrounds with the Fair buildings added I the background and look lifelike. Eventually, this sort of app could open the door to exploring the St. Louis of the 1910s-50s and beyond in a much more in-depth fashion than just looking at old photos and videos from that time. 

We'll never be able to go back, but for at least some time, we can imagine that we were there and maybe learn a thing or two.

^I'd say something, but a friend of yours and I are blowing up your Facebook thread, I think. Truth be told, I expect it would require a heck of a lot of money . . . but I really do like the idea. The folks over at Titanic Honor and Glory might be able to give you actual numbers, and they seem pretty approachable. What you're suggesting is, in many ways, more or less what they're doing with their virtual Titanic. And they've got a surprising amount of the ship modeled. The idea was history education. They decided to make a game out of it. It's . . . mostly? . . . crowd funded. (Maybe entirely.) And they have a demo on Steam you can check out. You might ask them.

I know how it could be done. The cost would all depend on how detailed you would want the experience to be. You also would be limited by the platform: your phone would probably not be able to handle the intense graphics, however a desktop powered VR system in the Missouri History Museum, for example, could provide a very immersive experience.