Rockopolis
An underground settlement and the safest places in The Capital Wasteland before Herbert "Daring" Dashwood and his stalwart Ghoul manservant Argyle let slavers from Paradise Falls to Rockopolis and killed everyone there. They used to be led by man named King Crag, and the only way in was by knowing a secret knock
To bad Dashwood got Rockopolis destroyed, it would have made a great place to live.