If that was possible, I would probably choose to visit the Ancient Egypt because I have always been fascinated by that society.

If that were possible, I would probably choose to visit Ancient Egypt because I have always been fascinated by this society. Me too. You can say "this" or "that". They are equally correct. The only difference is inside your brain. If you think of it as something close, say "this". If you think of it as something far, say "that". You might think of it as being close, for example, if you have been thinking a lot about it lately. Since it is not possible, "were" is the correct word to use. "Was" is past tense. It is not grammatically wrong to use past tense but that is not the meaning that you want. It is not possible right now.

If that was possible, I probably choose to visit the Ancient Egypt because I always been fascinated by this society