Sibir

WHEN Ivan the Terrible, Tsar of Muscovy, Lord of Novgorod, and of Sibir, died some twenty years before, he left in the world two sons—an elder, Feodor and a lusty youngster Dmitri.

Source: wiktionary

Catherine the Great’s rule of thirty-four years was a period of expansion. Russian exploration and colonization spread through Sibir to North America, and the Russians occupied Alaska. […] After the mysterious death of Alexander I (many people believed he hid himself in Sibir for a number of years under the name of Theodore Kuzmitch) his younger brother, Nicholas, became the Emperor of Russia.

Source: wiktionary

“In the summer,” Lev informed him, “Sibir can be a most beautiful place.”

Source: wiktionary