Crowsnest

Foc’sle-head and forward deck lay engulfed to the fore-hatch. Crowsnests and rigging were crowded with human forms awaiting the end.

Source: wiktionary

Binoculars from the crowsnests and bridges / Of all the ships, escort and convoy, swept / The horizon: dots turned into lines, the lines / To hulls and decks and guns and turrets—five / British destroyers making thirty knots.

Source: wiktionary

At sea it can be seen through telescopes on all the crowsnests and lookout towers.

Source: wiktionary

hms Duncan had crowsnests and a slightly different shaped bridge which included provision for a radar cabin.

Source: wiktionary