https://www.britannica.com/technology/kremlin
網頁kremlin, Russian kreml, formerly kremnik, central fortress in medieval Russian cities, usually located at a strategic point along a river and separated from the surrounding parts of the city by a wooden—later a stone or brick—wall with ramparts, a moat, towers, and battlements. Several capitals of principalities (e.g., Moscow, Pskov, Novgorod, Smolensk, Rostov, …