You're likely referring to ziggurats, ancient Mesopotamian structures. These were massive stepped pyramids built of mudbrick, and sometimes faced with baked bricks, serving as temples dedicated to various deities.

Here's what you should know:

* Made of mudbrick: Ziggurats were primarily constructed using sun-dried mud bricks, a readily available and inexpensive building material in Mesopotamia.

* Stepped structure: They featured a series of ascending terraces, often culminating in a shrine at the top. The number of steps and the overall size varied depending on the specific ziggurat.

* Religious purpose: These towering structures served as temples, housing the statues of patron deities. Religious ceremonies, offerings, and pilgrimages were held at ziggurats.

Famous examples of ziggurats include:

* The Ziggurat of Ur: Located in modern-day Iraq, it was dedicated to the moon god Nanna.

* The Ziggurat of Etemenanki: In ancient Babylon, this structure was dedicated to the god Marduk and was believed to be the inspiration for the Biblical Tower of Babel.

While the term "stepped mountains made of brick-covered earth" is not a standard term, it accurately describes the physical features of a ziggurat. Let me know if you have any other questions about ziggurats or ancient Mesopotamian architecture!