This is my impression of a Greek amphitheatre (or amphitheater if you live in the USA), where plays and performances were shown. Often these were built into a natural hillside.
The model is a low poly game asset, with a number of PBR texture files that can be tuned in size to your liking. I tried to make it look naturally weathered, with murals on the large walls at the front and a tiled mosaic on the stage to add interest. The dirt plane ground can be removed if you're putting it into a game, and replaced with your preferred terrain - that's what I did in the game I'm working on. I added it more as an example than anything. Though, it might still come in handy for you.
STL (Stereolithography, filesize: 136 KB), OBJ (OBJ, filesize: 172 KB), TEXTURES (Textures, filesize: 175 MB), 3DS (3D Studio, filesize: 93 KB), FBX (Autodesk FBX, filesize: 169 KB), C4D (Cinema 4D, filesize: 544 KB), UNITYPACKAGE (Unity 3D, filesize: 253 MB)