In 1652, Ivan Pokhabov built a zimovyo (winter quarters) near the site of Irkutsk for gold trading and for the collection of fur taxes from the Buryats. In 1661, Yakov Pokhabov built an ostrog nearby. The ostrog gained official town rights from the government in 1686. The first road connection between Moscow and Irkutsk, the Siberian Road, was built in 1760, and benefited the town economy. Many new products, often imported from China via Kyakhta, became widely available in Irkutsk for the first time, including gold, diamonds, fur, wood, silk, and tea. In 1821, as part of the Speransky reforms, Siberia was administratively divided at the Yenisei River and Irkutsk became the seat of the Governor-General of East Siberia.
Lake Baikal is the largest freshwater lake by volume in the world, containing roughly 20% of the world's unfrozen surface fresh water. With a maximum depth of 1,642 m (5,387 ft), Baikal is the world's deepest lake. It is considered among the world's clearest lakes and is considered the world's oldest lake — at 25 million years. It is the seventh-largest lake in the world by surface area. With 23,615.39 km3 (5,700 cu mi) of fresh water, it contains more water than all the North American Great Lakes combined.