1) Abysses 1) Big bays 2) California and Mexico 3) Chasms 4) Deep chasms 5) Gaps to be bridged 6) Large bays 7) Large bodies of water 8) Mexico and Panama 9) Partly enclosed ocean areas 10) Persian and Mexico, for two 11) Rope bridge sites 12) Unbridgable gaps 13) Vast distances 14) Wide gaps 15) Wide separations