What features does every map in Don't Starve have?

Question

As far as I know, every default Reign of Giants map has the following:

• At least one instance of every biome
• At least one Pig King.
• At least one (usually 2-3) Totally Normal Trees
• Maxwell's Door, and the five "Things" used to activate it.

What other special game elements are spawned naturally in every map?

By "special", I am ignoring things like type of tree, monsters, plants, boons, etc. Including all of those would make this question far too open.

I am thinking of set pieces or unique items -- things like:

• Glommer's Statue
• The small farm set piece (several Basic farms, carrots, twigs, and grass tufts, and usually (always?) the Metal Potato Thing)
• Pig village(s)
• Mandrakes -- the only non-unique item I'm including on this list
• The Eye Bone
• Others....??

Answer 1

I can't list all of them for sure, but I know there is always 3 plugged sinkholes, which lead to the caves. One spawns in the birchnut forest, near pig king. One spawns somewhere in the patchwork biome. One spawns in a forest in the center of your swamp. Some guy in the comments of the wiki page on wormholes also said there's 3 pairs of wormholes per world, but I'm not sure if that's true.