All this talk of Gondor=Venice has brought something to mind.
I think Tolkien means that Gondor the country is like Venice in its political structure - a city state controlling smaller vassals. But where does Minas Tirith remind me of? Oxford.
This is quite odd, as Oxford has its own Bridge of Sighs, which links the two parts of Hertford College over New College Lane; this in fact looks like The
Rialto Bridge in Venice, not the Bridge of Sighs. Oxford is also known for its canal and rivers like Venice, and is quite a 'watery' place. Even the buildings are quite Venetian at times - the old Bodleian in particular has that ancient crumbling air to it (though it is not crumbling
), and the Sheldonian Theatre is also very Italian (and it also looks creepy to me).
It's Oxford's twisting alleys, ancient buildings and air of monumentality make me think of it as a flat Minas Tirith. The half-hidden quads also conjour up an image of Minas Tirith with hidden courtyards within buildings. And then there's the Radcliffe Camera, the neo-classical Hawksmoor designed extension to the Bodleian. This is Tolkien's inspiration for Sauron's temple to Melkor on Numenor...