*OATH
Feudal system
*OBSERVED
Galileo Galilei
*OCCURRED
Nostradamus
*OCCURS
File Maker
*OFFICIALLY
Constantinople
Spanish Inquisition
*OFFSET
Bell-Tower Mechanism
*OFTEN
Oil paints
*OIL
Oil paints
*OLDEST
Bell-Tower Mechanism
*ONCE
Copernicus, Nicolaus
File Maker
Gun
Joint
Viola-Organista
*ONE
Ball Bearings
Bobbin Threader
Copernicus, Nicolaus
Drawbridge
Dredger
Drums III
Henry VIII
Last Supper, The
Magellan, Ferdinand
Middle Ages
Milan
Raphael
Verrocchio, Andrea
Walking Buoys
*ONES
Drawing Compasses
*ONLOOKERS
Rocket
*ONTO
Bobbin Threader
Bridge Canal
Parachute
*OPEN
Joint
*OPENED
Botticelli, Sandro
Drums II
*OPENINGS
Bridge Canal
Recorder
*OPENS
Bomb
*OPERATE
Tank
*OPERATED
Tank
*OPERATOR
Lifting
Windlass
*OPPOSITION
Copernicus, Nicolaus
*ORDER
Feudal system
*ORDINARY
Luther, Martin
*ORGANISTA
Viola-Organista
*ORGANIZED
Workshop
*ORIGINAL
Bell-Tower Mechanism
*ORIGINALLY
Wheel Lock
*ORLEANS
Hundred Years' War
Joan of Arc
*OTHER
Drawing Compasses
Florence
Italy
*OTHERS
Tank
*OTHERWISE
Life Preserver
*OTTOMAN
Constantinople
Suleiman the Magnificent
*OUTBREAKS
Black Plague
*OUTFIT
Diving Suit
*OUTLINED
Renaissance
*OUTLINES
Machiavelli, Niccolò
*OUTLYING
City-state
*OUTSIDE
Bell
Reciprocating-to-Rotary
*OVER
Cortés, Hernán
Drums III
Gama, Vasco da
Gutenberg, Johannes
Helicopter
Hundred Years' War
Joan of Arc
Walking Buoys
Wood Planer
*OVERPASS
Bridge Canal
*OVERSAW
Henry VIII
*OVERTHROWN
Sforza, Lodovico
*OWN
Botticelli, Sandro
*