1. Build and oversee a community in the Yucatan peninsula, isolate [no roads] only access is by air [4800 ft air strip] and a seaport. This community will be isolated from the rest of the area and can support 1200-1500 people. Eventually this community will sustain itself [farming, solar power, research] with the primary purpose being research into social and utopian principles and organization models. A real-life Dharma Initiative except not on an island [however there are mysterious water filled tunnels and sink holes nearby].
2. Build a self-sufficient man-made island on an atoll in the south pacific for the purpose of commerce. This island will be a finance and technology hub with the primary driver being a constitution and set of laws that are very favorable to monetary / patent freedom. Think of this as a new south pacific version of Switzerland complete with airstrip, sea port and several huge resort properties and 100+ story office/living space buildings.
3. Conceive of and develop a series of technologies needed for a far more sustainable set of living principles. The idea of creating tools needed for a family or small group of people to live completely off the grid for years with no need for help or resources from the outside.
Rough budget for these projects is 2-4 billion USD. Which of the three would you choose and why? If you succeed after a 5 year period of time, you will have access to unlimited monies in perpetuity.