Thank you for your question! 🙂
Short answer: when you self transform, you are establishing heaven before destruction. Right? Through the law of karma, you will experience heaven in the future and through your stage you will experience that “now” as well. That is the sign that we can “see.”
If you are referring to physical facilities, then your question would have been very tough to answer in the 1950’s, when there was no knowledge of the “Advance party.”
Now, since BapDada has disclosed this, then we know that there are some souls who are doing these things in a very incognito way. Once destruction happens there will be still 35 years before you see the “final product.” That is plenty of time to build things.