Sargassos

The Sargasso Sea is frequently (but erroneously) depicted in fiction as a dangerous area where ships are mired in weed for centuries, unable to escape.
-copied from here.

I expected Poul Anderson's "Sargasso of Lost Starships" to be a hard sf story about wrecked or abandoned spaceships congregating somewhere like a Lagrangian point. (For Lagrangian points in Anderson's Technic History, see The Beginning Of Technic Civilization.) Instead, it is almost fantasy-with-spaceships: physically beautiful, psychically powerful humanoids hijack spaceships in the Black Nebula. "Sargasso" has come to mean a place where ships disappear.

In James Blish's "Sargasso of Lost Cities":

the cities, protected by force fields, fly between stars faster than light and thus are "starships";

however, they are not lost but instead have congregated in a common orbit because they have been impoverished by an interstellar economic depression.

Anderson's and Blish's titles are almost interchangeable. Each of these works is incorporated into its author's main future history series.