The Kremlin is 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, when a host of Italian builders arrived in Moscow at the invitation of Ivan III the Great. Of the most important towers, the Saviour (Spasskaya) Tower leading to Red Square was built in 1491 by Pietro Solario, who designed most of the main towers; its belfry was added in 1624-25. The chimes of its clock are broadcast by radio as a time signal to the whole nation. Also on the Red Square front is the St. Nicholas (Nikolskaya) Tower, built originally in 1491 and rebuilt in 1806. The two other principal gate towers--the Trinity (Troitskaya) Tower, with a bridge and outer barbican (the Kutafya Tower), and the Borovitskaya Tower--lie on the western wall.…