Aristolochia gigantea has I think the largest flowers of any climber grown in mediterranean climates, up to about 40cm across. The spectacular flowers have the bonus of an attractive faintly lemony scent (not to be confused with the vile stench of its rather similarly named cousin A. grandiflora). We grow it in our southern Greek garden on a high south-facing wall. It is extremely strong-growing, really quite a strangler, apparently reaching up to 30 metres in the wild - we have to cut it back ruthlessly each year to keep it reasonably within bounds. I have also seen it growing in the south of France and Spain, and Oron Peri has it in his Israel garden.
We irrigated it originally. It is now no longer watered, but I suspect that its greedy roots may have reached over to tap the water that a lime tree gets, growing a few metres away.
The little white flower is of a very appealing climber we grow with it, Pandorea jasminoides 'Red Eyes'.