The Golan Heights
This is an area of great international significance. The majority of this territory was captured by Israel during the 6 Day War in 1967. This area is still not internationally recognised as Israel and is considered to be under Israeli occupation.
However, for practical purposes if you want to visit the area, it is controlled by Israel - you can access it easily from within Israel with no permit, border check, or anything, but it is completely inaccessible from Syria.