Galactic core

From Memory Alpha, the free Star Trek reference.

The galactic core is the central region of the Milky Way Galaxy. Anchored by a supermassive black hole, it is subject to intense radiation and increased risk of astronomical near-misses (resulting in climate change on the local planets) which makes life unlikely to prosper in the region. Despite these troubles for life, at least one advanced species has been discovered near the galactic core, the Cytherians. The core is surrounded by an immense energy field called The Great Barrier.

In 2269, the Enterprise, while on a scientific mission to find the creation point in the Galactic core, found an entrance to an alternate universe where magic replaced science. (TAS: "The Magicks of Megas-Tu")

The Magnetic organism planned to use the Enterprise to head for the galactic core in the hopes of taking over the galaxy. (TAS: "Beyond the Farthest Star")

The mythological planet of Sha Ka Ree was discovered near the galactic core in 2286 by the vulcan Sybok on board the Enterprise-A. (Star Trek V: The Final Frontier)