mesa's
Unusual flat-topped seamounts in the ocean are called Guyots. Guyots are submerged volcanic mountains with a flat top that has been eroded by waves and currents over time.
Plateaux.
The Arkenu Mountains, deep in the Libyan desert are flat topped mountains that rise to about 5,000 ft.
A flat topped flower cluster is called a corymb or a cyme.
There are actually three different names that can be used to describe a high, flat topped mountain or hill. These names are plateau, mesa, and butte. These flat top mountains are also called Tepui (or tepuy) in the native language of the Pemon, the original inhabitants of the Gran Sabana area in Venezuela. It means "house of the gods".
A flat topped mud brick tomb is called a mastaba.
A pie with no top crust is called an open-faced or open-topped pie.
A submerged flat-topped peak is called a "seamount." Seamounts are underwater mountains that rise from the ocean floor but do not reach the water's surface. They typically have a steep slope and a flat summit, and they are often formed by volcanic activity. Seamounts can host diverse marine ecosystems and are important for ocean biodiversity.
A flat-topped elevated landform is called a plateau. Plateaus are high areas of land with a relatively flat top and steep sides. They are often found between mountains or hills and can be formed through geological processes such as uplift, volcanic activity, or erosion.
ziggurat
Cyme
The Cahokia civilization in North America is known for their flat-topped mounds.