Megalith and Obelisk

Megalith noun - Memorial consisting of a very large stone forming part of a prehistoric structure (especially in western Europe).

Obelisk and megalith are semantically related. In some cases you can use "Obelisk" instead a noun "Megalith".

Obelisk noun - A stone pillar having a rectangular cross section tapering towards a pyramidal top.

Megalith and obelisk are semantically related. Sometimes you can use "Megalith" instead a noun "Obelisk".