Location from deaths-end by
The abandoned ghost-station at the Sun-Jupiter L2 point, built around a microscopic black hole that should have lowered the speed of light around the Solar System.
Lightspeed II was one of the two major black-domain research stations of the Bunker Era — a project to lower the speed of light through vacuum and so render the Solar System invisibly safe to dark-forest hunters. Its centerpiece accomplishment was moving Leda from her Jovian orbit, compressing her down to a microscopic Schwarzschild radius, and beginning to feed the resulting black hole. The project was canceled in favor of the Bunker Plan and the city was emptied. By the time Cheng Xin visits with Cao Bin, the air inside is stale and the apparatus is exquisite and abandoned.
A non-rotating gray ring-city, three kilometers across, drifting silently at L2 with the Sun and Jupiter in fixed alignment. Its skin is cracked open in places, exposing internal frames. No interior lights. At the dead center, suspended in vacuum behind massive electromagnetic baffles, a microscopic black hole — twenty nanometers across, the mass of the Jovian moon Leda — surrounded by the still warm wreckage of the experiment that fed it.