Pushing for Megalithism to erect menhirs, dolmens and the like in the Neolithic and onward, will ask for a relative great deal of your population in manpower. In the early stage of the game, it may keep your people from completing other tasks that are vital to survival.
Menhirs and carved statues come in 3 shapes; the ‘father’, ‘mother’ and ‘child’ and need one megalith rock to erect either of these. All other megalith structures require 3 or more. Besides boosting your settlement with prestige, these stone monuments also offer happiness to your people, onto which they can up their morale levels. Other non-monumental objects, skull and totem poles, banners offer that as well, besides being able to bury the dead inside burial mounds, dolmens and cairns.
The stone henges you can build look pretty much like the real thing, and come in two not too different looking versions.
Look for purple-ish rocks while roaming in primal vision mode to find and pick them loose.
Supplying it with 3 leather skins and 3 logs and your rolling megalith can get going. When it has arrived, 2 of the 3 materials will be returned. Megalith structures can be recycled, but also return less megaliths than were required to build it. It is advised not to get multiple megaliths rolling at the same time until you have a large enough workforce to be able to. Megaliths can be pulled by one single person, though make sure they can make it home to bread and bed in time, or quite a few may suffer and die.