Tower

A tower is a high structure, usually man-made. (Though the sea can erode the land and make a tower or pillar.)

The Eiffel Tower.

Purposes of the large height (a tower may have multiple purposes):

being impressive and beautiful
saving surface area
for the view
- for tourism
- for guiding: traffic control tower, in particular at an airport
- for security against coming in or getting out: a watch tower at a prison, concentration camp, fortress/castle, border/defensive wall; in some of these cases also to fire from;
- for watching out for fire, especially in a forest: fire tower;
for spreading light: light tower, lighthouse
for spreading sound: church tower with church bells, minaret of a mosque
antenna tower
for use of the gravity: water tower
as part of a suspension bridge or cable-stayed bridge
for supporting power and signal cables
in a swimming pool for jumping from a height
for fun of climbing in it, for example on a children's playground
the tower of a high slide, for supporting it and with stairs for reaching the starting point
to gain access for maintenance or cleaning, e.g. scaffold tower
for attacking a walled city: siege tower
to reach heaven (legendary Tower of Babel)
for some unknown reason, skyscrapers aren't thought of as towers.

A tower wagon is a mobile tower for construction work, firefighting, rescue work, window cleaning, filming, etc.