Zion
2 of the 7 encyclopedias on this shelf carry an entry for Zion. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
or SION, the highest and most S. mount of Jerusalem; rising about 2,500 feet above the Mediterranean, and from 200 to 300 feet above the valleys at its base. It was separated from Akra on the N. and Moriah on the N. W. by the Valley Tyropœon; and had the valley of Gibbon on the W., that of Hinnom on the S., and that of the Kidron on the S. E. It was a fortified town of the Jebusites till subdued by David, and thence forward was called the "City of David." A mosque near its S. brow now covers the "tomb of David" so called, most jealously guarded by the Mohammedans. This mount, together with Moriah and Ophel, was inclosed by the first wall, and fortified by citadels. On it were erected the magnificent palaces of Solomon, and long afterward those of Herod. At the present day a considerable portion of it lies outside of the modern wall on the S. "Zion," and "the daughter of Zion," are sometimes used in Scripture to denote the whole city, including especially Moriah and the Temple; and sometimes figuratively for the seat of the true Church on earth and in heaven.
Aiton's Encyclopedia (1910)
zi'un, the loftiest of the hills on which the city of Jerusalem was built. It was occupied as a stronghold by the Jebusites before it was taken by King David and converted into a citadel. It rises abruptly some three hundred feet above the vale of Hinnom and Kidron. A Turkish mosque, said to shelter the tomb of David, now occupies the southern brow of Zion. The Old Testament writers frequently speak of Jerusalem as Zion and the Daughter of Zion. The prayer of the Hebrew exiles in Babylonia was to be restored to Zion. The name is used also by modern writers to designate the kingdom of God both on earth and in heaven.