gorge, strait, ravine, isthmus
峽 centers on a narrow passage through terrain: a gorge, ravine, strait, or isthmus—any place where land or water is squeezed between two sides.
峽 combines 山 (mountain) with 夾, which likely contributes both sound and the idea of being pressed between two sides, reflecting a narrow mountain passage.
The left side 山 means mountain, and the right side 夾 looks like a person squeezed between two sides. Picture a narrow gorge where mountains press in from both sides, leaving only a tight passage.
For キョウ, imagine a narrow gorge in Kyoto (キョウト) where the mountains close in: Kyoto -> キョウ, and the gorge is a famous sight.