Vast ancient empirofixed hyperdimensional megastructures scattered throughout part of the known universe (and presumably beyond), built by a race called the First Ones, but then all progenitor races are called First Ones.
These giant structures that span zones and allow ships to traverse FTL without a hyperspace “jumpdrive” (the structure itself converts the ship to paraspace).
Being hyperdimensional, they span a number of ontological degrees or zones, and allow access to hyperspace and beyond without shipboard orthogonal transrotation. Protected and maintained by elvish caretakers, often associated with minor or major celestials, considered sacred and used as a confluence by many alien races; different orders of beings live on the different levels. Each meru is the center of a vast cluster of orbital habitats, zeegee docks, and other facilities.
Relative to jump gates, Merus are far elaborate, vast, multizonal structures, built by a progenitor race and positioned in important libration points across the known universe. Careful controls on transit to avoid paradoxes (see Causality Protection). They are of great strategic importance, serving as major trade routes in peace time and military choke points in war.
Inspired by Terminal World by Alastair Reynolds