You're describing a steppe or prairie. These are vast, flat grasslands that gradually increase in elevation, often forming rolling hills or a plateau.

Here's a breakdown:

* Steppe: This term is commonly used for grasslands in Eurasia, particularly in Central Asia. These steppes often have semi-arid conditions with hot summers and cold winters.

* Prairie: This term is more commonly used for grasslands in North America, particularly in the Great Plains. Prairies can be quite diverse, ranging from tallgrass prairies to shortgrass prairies.

While the term "grassland" can be used to describe both steppes and prairies, the terms "steppe" and "prairie" often have specific connotations related to their geographical location and specific environmental conditions.

Let me know if you'd like more details about specific types of steppes or prairies.