The High Energy Stereoscopic System (HESS) telescope system in Namibia discovered a new source of very-high-energy gamma-rays from the direction of the globular cluster Terzan 5. Being very likely located in the outer parts of Terzan 5, this source is the first example of gamma-ray emissions from a globular cluster. The off-center position of the source and the specific origin of the gamma-rays pose a puzzle for scientists.