Black
The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia.
Gravitational lensing has been used for the first time to detect and measure an inactive black hole. The door is now open to study the largest black holes in the universe. "Gravitational lensing events are rare, but are most prevalent in the most massive galaxies, that host the largest black holes."