These are located between 1 and 4 levels above the Vibrating Square level (and therefore between the 15th and 22nd levels of Gehennom, and between DL 40 and DL 51).
The level without the portal is eligible to leave bones files; the level with the portal is not.
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This core of the level is surrounded by normal Gehennom-like maze; the walls are diggable.
These towers are found on two levels; one tower contains a magic portal leading to the bottom level of the (real) Wizard's Tower at the point marked 'x', the other does not (an amulet being there instead). Both contain four squeaky boards (marked), a vampire lord, and a random L; a single kraken is found in the moat of each.
The name "fake wizard's towers" is a reference to earlier versions in which the Wizard of Yendor lived in a similar structure surrounded by maze; these days, he lives in a similar structure surrounded by a much larger tower. Such is upward mobility.