The fortified citadel of medieval Russia. The term also applies to those in medieval Slavic towns. The most famous and best-preserved is the one in Moscow, which is a rare stone-built example. Within it lie a variety of palaces, churches and state buildings in a range of styles spanning the 14th-18th centuries. Archaeological work has revealed that in 1156 Prince Dolgoruky built the first fortifications - ditches and earthen ramparts topped by a wooden wall with blockhouses. The origin of the word kremlin is disputed; some authorities suggest Greek words for citadel" or "steepness others the early Russian word krem, meaning a conifer providing timber suitable for building. The fortified enclosure of the Kremlin, the symbol of first Russian and later Soviet power and authority. Its crenellated red brick walls and 20 towers were built at the end of the 15th century, by Italian builders hired by Ivan III the Great.