MenegrothMenegroth - The capital of the Sindarin Kingdom of Doriath.  With the Great Journey, and subsequent Sundering of the Elves, some stayed behind in Middle-earth and made it their home.  The Elves in Beleriand became the Sindar and their king was Thingol.  He built Menegroth with the help of the Dwarves.

 

"Therefore the Naugrim (Dwarves) laboured long and gladly for Thingol, and devised for him mansions after the fashion of their people, delved deep in the earth.  Where the Esgalduin flowed down, and parted Neldoreth from Region, there rose in the midst of the forest a rocky hill, and the river ran at its feet.  They made the gates of the hall of Thingol, and they built a bridge of stone over the river, by which alone the gates could be entered.  Beyond the gates wide passages ran down to high halls and chambers that were hewn to the living stone, so many and so great that that dwelling was named Menegroth, the Thousand Caves." ~The Silmarillion, chap. 10 (Of the Sindar)