A sailing ship, used for war and trading, remove an e and I'm a unit of liquid capacity.

A song by Yes. Add an s for a book by RAH, a movie trilogy or a video game. The first word is what Jefferson Airplane became, the second is what your boss says you are if you come in on the weekend to help solve the problem he created

Beneath the waves I made my bed, yet legends keep me far from dead.

Once my towers touched the sky, now fish swim where they used to lie. Though many seek, few claim they’ve found, a city lost but still renowned.

Diogenes carried me without owning me. Zeno could never finish crossing me. Borges filled me with libraries, yet left me unexplored. Empires claimed me, cartographers scarred me. I am measured but never held, occupied yet never grasped, divided but never cut. Every kingdom begins with me, and every grave receives me. What am I?