Piazza del Duomo and the striped cathedral at blue hour

Siena's cathedral is banded in white and dark green marble from the ground to the top of the campanile, which makes it the most graphic building in Tuscany. In daylight that pattern fights with everything else in the frame; under the floodlights at dusk it becomes clean geometry, and the piazza in front turns into a stage.

The strongest position is on the far side of the square, near the entrance of the Santa Maria della Scala hospital, where the whole facade fits in without extreme wide-angle distortion. A second, quieter frame is the sloping lane down the side of the cathedral towards the baptistery, where the striped wall runs away in perspective and the steps give a natural place to sit.

Blue hour here is short and precise: the lights come on before the sky has gone black, and you have perhaps twenty minutes when both read. The piazza is enclosed and dead quiet at that hour, which makes it one of the few famous cathedral squares in Italy where a proposal is genuinely private.