“A gallows fifty cubits high”
Have them build a gallows fifty cubits high, and ask the king in the morning to have Mordecai hanged on it. (Esther 5:14 BSB)
What it sounds like today
A wooden gallows with a hangman's noose, as in a Western hanging.
The cultural key
'Gallows' conjures a scaffold and a rope, but the Hebrew word is just 'tree' or 'pole' (etz), and the Persians executed by impalement, driving a sharpened stake through the body, or by fastening the corpse high on a pole for all to see. Haman is building an impaling stake, and its absurd height, fifty cubits (some seventy-five feet), is the whole point: he wants Mordecai's death displayed above the entire city as a monument to his triumph. The grim justice the book relishes is that Haman is impaled on his own stake (7:10). Picturing a tidy hangman's gallows softens both the Persian brutality and the poetry of a man skewered on the device he built for his enemy.
Recovered meaning
The 'gallows' is really a towering impaling stake for public display, Persian-style, not a hangman's scaffold. Haman builds it for Mordecai and ends up impaled on it himself.