Like any old city Kiev had a strong fortification system in the past. Big fortresses were built in the 10^th-13^th, 15^th-17^th centuries, but all of them have not survived, and only some elements of the last one that was constructed in the 18^th – 19^th centuries still can be seen in the city. The construction lasted from 1709 till 1870 in the Pechersk area (the territory around the Kiev Cave Monastery) and occupied a very big territory. The construction started under the personal supervision of the Russian Tsar Peter the Great and Hetman of Ukraine Ivan Mazepa on the ramparts of the Cossack wooden-earth fortress that surrounded the Monastery (1679). Hundreds of people who lived in this area were moved to other parts of the city and almost half of the city was destroyed to realize the grand plans. The bastions were constructed according to the ideas of the legendary French engineer Sebastian Vauban. It was a very complicated system of high earth ramparts (10-15 m high) that were cut by bricked 40 metre long tunnels. Like any other fortress it had numerous underground corridors and premises, many barracks and  bastions on the surface. Pretty soon the fortress became the biggest in Europe and Kiev was the most fortified city of Russian Empire. Some historians declare that it was the Kiev fortress that made Napoleon decline the attack on march in the direction of Kiev in 1812 and to direct his army towards Moscow. It might sound strange but this fortress never participated in any military action and no gun-shot was ever made. To the end of  the 19^th century it lost its military significance, gradually some of its buildings were used by different offices, some were destroyed,  and the biggest caponier  in 1863 was turned into a prison for political suspects. Here in 1927 the museum was opened, to-day it numbers more than 17 000 exhibits, among them one can find authentic documents, maps, decorations, weapons, uniforms, personal belongings of the prisoners, a carriage that took prisoners to the death penalty place. The museum workers continue the research works because the fortress is still not fully investigated and there are many unknown pages to be opened.