A cache in the "Jaffa Slope" park which will take you close by the water and explain what are the weird poles you see all around you.
One of the commandments for Shabat (Saturday) is to rest and do no work, including carrying things around. This poses a problem, as people want to go outside to visit friends or the synagogue, and they can't take anything with them, including prayer books ("Sidur") or the baby strollers. However, only carrying things from your own house outside is prohibited while moving them around inside your property is OK. So, the solution to this problem was to turn the entire area into one single unit, in which moving things around is permitted. This resembles buildings in the middle ages, that were build in a squared formation with surrounding a yard, which is considered part of the building. The physical way to encompass a perimeter is using wires such as the one you are seeing in GZ. In fact, all Israeli Jewish cities and villages are surrounded by this wire called "Eruv wire" (חוט עירוב) which turns them into one big private property where carrying things is permitted in Shabat. Usually the wires are stretched between existing infrastructure, such as electricity poles or road signs, but when there are absent - a pole is posted just for it. Every Friday the local Rabbinate is inspecting the integrity of the wire and fix it if needed, to make sure the Shabat is properly observed.
The last paragraph is based on personal knowledge. You can read more "certified" info on wikipedia: https://en.wikipedia.org/wiki/Eruv
Now, go get the cache and watch your step (especially in the dark)!