Its 2.4-hectare footprint is smaller than that of the other surviving medieval kremlins, however. The latest Kremlins were instituted in 1921. Some of the churches, kremlins and monasteries are declared as World Heritage by UNESCO. Stone and wooden kremlins of the towns were also included in the Great Abatis Line. Some kremlins in Russia are called "detinets", as for example the Novgorod Detinets.