altaltissimo
The highest point of something; the pinnacle or apex.
countable, literary, rare, uncountable
Then one shall propose (in a speech, curt Tuscan, / Sober, expurgate, spare of an "issimo,") / Ending our half-told tale of Cambuscan, / Turning the Bell-tower's altaltissimo.
Where it comes from
Probably derived from Italian alto + altissimo.
Adapted from the Wiktionary entry altaltissimo (CC BY-SA 4.0).