The Golanans were a technologically advanced species which lived on the planet Golana, in the Alpha Quadrant. One of their technological achievements was their time portals. They went extinct about two thousand years before 2374.
In the 24th century, the ruins of this long-dead species were discovered by the Bajorans as they colonized Golana. Throughout the century, these ruins were studied by archaeologists. (DS9: "Time's Orphan")