Gravestone and Landmark

Gravestone noun - A shaped stone laid over or erected near a grave and usually bearing an inscription to identify and preserve the memory of the deceased.

Landmark and gravestone are semantically related. In some cases you can use "Landmark" instead a noun "Gravestone".

Landmark noun - A point in a chain of events at which an important change (as in one's fortunes) occurs.

Gravestone and landmark are semantically related. Sometimes you can use "Gravestone" instead a noun "Landmark".