Usopp best terrain?

[Warmmedown]

Which place would he be able to take on the strongest opponents, one-on-one?

Skypeia's cloudforest (does it rain there?)?
Water 7's Galley-la building (where some of the crew first fought CP9)?
Syrup Village?
Arabasta desert?
Where he fought Luffy?
Elbaf?
Elsewhere?