Tower

A tower is a vertical column.

There are a number of (physical) towers in NetHack:
 * A tower of flame - The physical effect of a fire trap, magic trap or chest trap, or the effect of reading a scroll of fire
 * Vlad's Tower - accessed via an upstair in Gehennom, with Vlad the Impaler carrying the Candelabrum of Invocation
 * Fake Wizard's Tower - A 3-level tower accessed from lowest level to highest in Gehennom, they are identical to the Wizard's Tower except for the final room, where there is a random amulet rather than the Wizard of Yendor carrying the Book of the Dead
 * Wizard's Tower - A 3-level tower accessed from lowest level to highest in Gehennom, this tower contains the Wizard and Book of the Dead
 * The Lonely Tower - The home level of the Wizard quest
 * The Tower of Darkness - The seek level of the Wizard quest
 * Additional towers are added in the Castle as part of the SLethe patch
 * As part of the Yeoman quest in SLASH'EM, there is a tower based on the real-life Tower of London
 * The Tower of the Dark Lord - The home level of the Necromacer quest in SLASH'EM
 * References (but not official ones) are made to any use in castles - the corners of the special level Castle as well as the home level of the Knight quest, Camelot Castle.

Encyclopaedia entry
Towers (_brooding_, _dark_) stand alone in Waste Areas and almost always belong to Wizards. All are several stories high, round, doorless, virtually windowless, and composed of smooth blocks of masonry that make them very hard to climb. [...] You will have to go to a Tower and then break into it at some point towards the end of your Tour. [ The Tough Guide to Fantasyland, by Diana Wynne Jones ]