A siege is a prolonged military assault and blockade[?] on a city or fortress[?] with the intent of conquering by force or attrition[?].
Sieges usually involve surrounding the target and blocking the provision of supplies.
... Tate Britain and Tate Modern
Victoria and Albert Museum
Merseyside
Customs & Excise National Museum[?]
Historic Warships[?], Birkenhead
Lady Lever Art ...