Short answers, pulled from the story.
The oldest known tower is the circular stone tower built into the walls of Neolithic Jericho, dating to approximately 8000 BC. Some of the earliest towers were also ziggurats, which appeared in Sumerian architecture from the 4th millennium BC onward.
A tower is distinguished from a mast by the absence of guy-wires, making it a self-supporting structure. It differs from a building in that it is not built to be habitable; its height serves a specific function such as surveillance, communication, or signaling.
The English word 'tower' comes from Old English 'torr', derived from Latin 'turris' via Old French 'tor'. The Latin and Greek forms were borrowed from a pre-Indo-European Mediterranean language, connected to Illyrian and Lydian place names and possibly to the ancient names for the Etruscans.
Three limits govern tower height: compressive failure (when the material can no longer bear the load), buckling under wind, and dynamic forces such as vortex shedding and seismic disturbance. Engineers address these through tapering the structure, placing supports at the periphery, and using tuned mass dampers.
Construction of the Leaning Tower of Pisa began in 1173 and was not completed until 1372, a span of nearly two centuries.
The CN Tower in Toronto, Ontario, Canada was built as a communications tower, designed to function as both a transmitter and a repeater.