This connection also recently has been suggested, with the sites Urbino - Pienza - Ferrara. It covers much of the same grounds as Town/city planning, but maybe we have to rename the connection to 'Renaissance Ideal City' (there can also be Industrial/Socialist Ideal Cities etc.)?

I would find it interesting to collapse all these categories into one as all aimed at an ideal city according to their concepts of what may constitute one.

But are not we just going to get the same list as in the T/C Planning "Category"?
By the way surely Saltaire should be in that Category too?
But I don't think that Shibam should be - I have no evidence that it was "planned" and, if the concept means anything there must be some over-arching scheme/concept - not something which grew organically which surely Shibam did.
Morelia (originally "Valladolid") in Mexico would seem to meet the Category criterion - as I understand it Philip II sent very definite instructions as to EXACTLY how cities were to be designed/built in the New world and that Morelia was the result.
Quote from the Web which conforms the notices scattered around Morelia's "Centro Historico"
"....Its harmoniously composed center is reminiscent of  Vicenza or Edinburgh's New Town. In the 16th century, King Philip II of Spain issued Las Ordenenzas, a set of urban-­planning ordinances regarding the layout of Hispanic American cities. According to these rules, each city should feature a main plaza bordered by four streets (Morelia, unusually, has two main plazas); the buildings facing the plaza should include ground-floor portals, arched semi­public spaces linking the buildings to the street."

I quite like the idea of a connection for Idealistic town designs -an alternative might be to reconsider whether the Category is at too "low" a level. But I can't immediately see an alterntive category for many of them - it does describe why they were inscribed.

So my proposal would be to build a connection Ideal Cities, including both Renaissance and Socialist examples. Any others?

Further I think I'd like to rename 'Town/City planning' to 'Urban Planning' as the latter is a more common term. It is used also prominently in the Unesco description of Shibam ("the earliest example of urban planning based on the principle of vertical construction").
And yes, Saltaire and Morelia should be in there too.

I've published the connection. Feel free to contribute. The difference between Ideal City and Urban Planning is still a bit hazy to me (the first probably is more utopian, the latter more practical).