Isaakievskiy Sobor (Saint Isaac's Cathedral), St. Petersburg

During the first part of the 19th Century, 11,000 serfs drove 25,000 wooden planks into the ground creating the foundation for what would become Isaakievskiy Sobor (Saint Isaac's Cathedral). More than 100 kilos of pure gold were used to gild the dome and the 112 polished granite columns to support it. The massive interior is constructed from various types of marble and stone and is designed to accommodate up to 14,000 people. Construction of the cathedral was a painstaking project, taking 40 years to complete; its architect, Auguste Ricard de Montferrand, died shortly after. The golden dome has governed the Neva River skyline for nearly 200 years. One of the cathedral's most popular attractions is its circular observation deck. After climbing 562 steps, a panoramic view of Peter's city awaits.