Apart from the Lottery etc... I would probably visit stone henge when it was built so see how the ****ers actualy did it.
Experimental history/archaeology has demonstrated that it's possible to:
i) Move the stones using heavy low-lying sledges during winter.
ii) Erect the uprights using well-known techniques.
iii) Place the top stones by building ramps.
It takes a
lot of work and it isn't fast, but it can be done in a simple enough way if you have a lot of people willing to work long and hard on it.
I'd rather know why than how. There are some clues and some theories, but the purpose isn't certain. We know it was very important to very many generations of people, but not why. Probably religious and probably about life and death, maybe the journey to the afterlife...but that's largely extrapolating from the obvious importance of the site. There was another henge upriver and it has been hypothesised that the river in between symbolised the journey to the afterlife...but nobody really knows.
I might also go back to Abraham and try to persuade him to not start his religion (and therefore the religions that spun off from it). If he existed.
But in reality, I'd use a one-shot deal to make myself rich. So yeah, lottery.