A permanent place to settle agreements

Sovereign land to all countries (maximum size is 1 mile x 2 miles, depending on size of the country).  This provides enough room for a private runway.  Gold can be stored by each country, although any form of value can settle agreements.

Covered settlement area provides privacy on the details, while ensuring all participants are safe.

EDIT:
Somewhere in this general area:

We'll need 'international corridors' from Mexico and the Gulf.  People can travel freely through those corridors without any documentation.

EDIT 2: