Planetary Gravity and its effects I live in Tunisia, exactly in Gafsa .. and there's a weird effect is happening, i really tried to ask people but no one had a clue, also i have seen that in other places on the internet.
If you put a car on a road, it ll twist towards the low place, which is obviously against gravity laws .. i don't know if there's a magnetic field which affects the car, but i should of tried another metal to be sure .. well anyways, it really interested me for years and i'm looking for an answer .
The video of someone recording this in my city : https://www.facebook.com/Tn.Rkike/videos/vb.354844837964783/833064886809440/?type=2&theater
 A: Video of a Gravity Hill
We have the same effect about 50 km from us, called "the magic road", as comment above says, it's an optical illusion, as you have only the sides of the road as a frame of reference.
Magic Roads

My first memory of the “fairy hill” phenomenon is as a child, reading an Enid Blyton novel in which there is a hill on which all cars stutter to a stop. Another such phenomenon is the fabled river where water runs upslope (such as at Fore Abbey) or the road where a car will roll uphill. There appears to be one of these oddities in most countries. (I came across a stream in Western NC many years ago that appeared to flow uphill — but strangely I’ve never been able to find it again.) 
Another, more scientific-sounding theory seems to appeal to younger generations less interested in fairy stories: this is that there’s a huge seam of copper under the road, and that this magnetically pulls the cars back uphill somehow.
The more rational-sounding explanation is quite simple: these are actually optical illusions. The roads only appear to be going downhill because of the surrounding landscape. The distant horizon is not visible at these spots, so the eye takes its cues for what is a flat surface, an up- or a downslope from the relationship between the visible landforms. These two roads appear to be going downhill, but really they’re each a gentle upslope, so when you stop your car and remove the brake, gravity takes over and pulls you gently backwards down the slope, even though to onlookers you appear to be traveling uphill.

