Lazar (, ), also known as Lazar the Serb or Lazar the Hilandarian (fl. 1404), was a Serbian Orthodox monk-scribe and horologist who invented and built the first known mechanical public clock in Russia in 1404. The clock, which also struck the hours, was built at the request of Grand Prince Vasily I of Moscow (r. 1389–1425). Prior to his arrival in Moscow, Lazar had served as a monk in the Serbian Hilandar monastery at Mount Athos. The clock tower was located in the palace behind the Cathedral of the Annunciation. However, the clock and the church in which it was located have not survived. Life A Serb, Lazar was born in the town of Prizren, in the Serbian Empire. He was a monk with the rank of crnorizac (, , černec) serving at the Serbian Orthodox Hilandar monastery, a centre of Serbian religious and secular culture and "the first Serbian university", located on Mount Athos. Lazar likely left Mount Athos as a result of the Rise of the Ottoman Empire. Russian (East Slavic) chronicles speak of Lazar, newly arrived from Serbia, inventing and building a clock on a tower in the Grand Prince's palace in Moscow behind the Cathedral of the Annunciation at the request of Vasily I, the Grand Prince of Moscow (r. 1389–1425). It was the first ever spring-driven (mechanical) clock, or striking clock, in Russia, and also the country's first public clock. The clock numbers were written in Church Slavonic. It was among the first ten such advanced clocks in Europe, and was regarded a technical miracle at the time. Clocks in urban towers, or municipal hour signals, did exist earlier in Italy, though it is not known how they indicated the hours. In 1344, Paduan chronicles confirmed an entirely new technology – a clock in a tower at the Paduan palace which automatically struck the hours (24h). The clock tower has not survived, and its exact location is undetermined, although it is believed to have been located at or near the Spasskaya Tower (formerly known as Frolovskaya). The clock was for a long time the only one in Moscow and Russia, and worked for more than two centuries without failure. It was then replaced by another clock which was destroyed in a fire. A miniature from the 16th-century Ostermanovskij manuscript (of the Litsevoy Collection of Chronicles, Ancient Chronicle, sheet 587, drawing 1175) exists which depicts