I-70 is concurrent with US-24 from the Colorado state line until US-24 splits at Levant and runs north of I-70. At Colby, I-70 begins to turn southeast until it reaches Oakley, where US-40 joins with I-70 for a concurrent journey through most of the state. Initially, the route remains high and unusually level as it follows a projection of the High Plains into the state. From Exit 140 (Riga Road), the route lowers from the High Plains into the Blue Hills region, as indicated by gentle undulations in the road and the unusual appearance of stone posts in the countryside. Approaching Russell, the route passes over three active sinkholes, the largest being the Crawford Sinkhole at Mile 179. Past Russell, the route follows a ridge between the Smoky Hill River and its tributary, the Saline River where the highway passes through the Smoky Hills Wind Farm. Reaching the county line between Russell and Ellsworth counties, the road begins to traverse the Smoky Hills.