stronghold

noun

1. A place built to withstand attack; a fortress.

   “AFter this victory thus opteyned by the Sicambris, they waxed so stronge that they wan frome yᵉ Almaynes dyuers Townes & stronge holds wᵗin Germania, and after that they opteyned yᵉ famous Cytie named Treueris; which as wytnessyth yᵉ Auctour of Cronica Cronicaruin, was firste foundyd in the Towne of the Patryarch Abraham before the Incarnation of Criste.”

   “For security's sake they [the Germans] gathered together in villages and cities. These they surrounded with heavy walls and towers, and protected them by castles, erected on steep cliffs and mountains. The custody of these strongholds was entrusted to the most efficient warriors, who in time formed a separate class, the nobility, from which the heads of the whole nation, the princes, kings and emperors were chosen.”

   “For a time, it was the only Royalist stronghold between London and Exeter, but it fell at last when a member of the garrison turned traitor and admitted the Parliamentary besiegers who destroyed it with gunpowder.”

   “As Edwin Clark [...] wrote in 1850: "[...] The lofty towers of the castle overhang the western approach to the Bridge, and the line passes into Conway through an opening pierced in the embattled wall, which entirely surrounds the town. These fortifications are in good preservation, and rank among the most perfect examples of the strongholds of the 13th century."”

2. (figuratively)A place of domination by, or refuge or survival of, a particular group or idea.

   “the last stronghold of the Cornish language”

   “With the numerous soldiers of Asia, with all of warlike stores, ships, and military engines, that wealth and power could command, the Turks at once resolved to crush an enemy, which creeping on by degrees, had from their stronghold in the Morea, acquired Thrace and Macedonia, and had led their armies even to the gates of Constantinople, while their extensive commercial relations gave every European nation an interest in their success.”

   “The Lord Mayor, in the stronghold of the mighty Mansion House, gave orders to his fifty cooks and butlers to keep Christmas as a Lord Mayor's household should; and even the little tailor, whom he had fined five shillings on the previous Monday for being drunk and blood-thirsty in the streets, stirred up to-morrow's pudding in his garret, while his lean wife and the baby sallied out to buy the beef.”

   “Bridge End is the border station and the scene of many a sad parting between enterprising shoppers and their purchases—for it is a stronghold of the Customs !—and half an hour is allowed in the timetable for examination and shunting.”

   “Thailand has been broadly split along north-south political lines since Thaksin [Shinawatra]'s ouster. A bastion of the conservative, pro-establishment Democrat Party, southern Thailand historically hosts much of the country's wealth and tourism. The poorer, agrarian north and northeast, where Thaksin's populist policies won him legions of supporters, remain Shinawatra strongholds.”