In my story, an ancient building has been abandoned for a whole century without any care or use from the inhabitants around. They refrain from approaching it because they believe it is cursed, which is why it hasn't been scavenged for resources.
The building is located near the sea on top of a hill, around 20 meters above sea level and 100 meters away from the coast. It doesn't get flooded but there is only grass surrounding it, nothing that would stop wind. The winters are mild, and the summers quite hot (mediterranean weather, I imagine it as north-west of greece in terms of temperature)
Here's a brief description:
The structure describes a large circle, whose floor is 4 meters (around 13 feet) under ground level, it has no roof, no windows and does not go above ground level (consider it as a well). It has a 40 meters diameter (~130 feet), the wall is entirely covered in stone held by mortar, while the floor is a mix of stone and large metallic shapes incrustations. Those shapes are made of copper. There is one stairway large enough for 4 men to walk side-by side, made of the same stones+mortar. It is not very steep and protuberates from the circle by a few meters. It connects to a dirt path.
After a whole century, exposed to wind, rain, what would this building look like?