Ostia

Ostia, the seaport of ancient Rome, at the mouth of the Tiber, now in ruins.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)

Ostend * Ostracism
O'Shaughnessy, Arthur
Osiander, Andreas
Osiris
Osmanlis
Osmose
Osnabrück
Ossa
Ossian
Ostade, Adrian
Ostend
Ostia
Ostracism
Ostrogoths
Oswald, St.
Oswego
Oswestry
Otago
Othman
Othman
Otho
Otis, James