The Earth does not have uniform density, therefore the force of gravity from the Earth's mass is not quite the same in all directions.

There is an area over Madagascar where gravity is somewhat stronger. This is referred to as "gravity well". It is used as a temporary storage location for inactive satellites, as they remain in geostationary orbit over this region with very little maintenance.

-it's a fact!

thanks to Fruan, who lives in a nuclear-free zone and inspired me to node science facts today.