The capital was moved to now-Nur-Sultan in the early 1990s, partly to ensure the northern parts of Kazakhstan wouldn't choose to leave the new country and rejoin Russia. One part of Kazakhstan is already arguably geographically part of Eastern Europe, as it sits west of what natural border? (edited at 5:18 pm, April 11, 2020 (EDT))
Original question: The capital was moved to now-Nur-Sultan in the early 1990s, partly to ensure the northern parts of Kazakhstan wouldn't choose to leave the new country and rejoin Russia. One part of Kazakhstan is already arguably geographically part Eastern Europe, as it sits west of what natural border?
Ural River