Porta Asinaria is very impressive and reminds me of the Roman walls around the old city of Le Mans. I refer to Roman-inspired structures in my books and use my holiday snaps of Roman France for inspiration: Nimes, Vaison la Romaine, Orange, Aix en Provence.
I'm embarassed that I haven't got to Rome yet, but intend to remedy this next year...

As for other visual clues, I have to have them: people, scenes even. I once got asked by a fellow passenger on the way to Charing Cross what I thought I was doing when I was jotting down an exquisitely cringeworthy conversation and making notes of the speakers' appearance. I have become more discreet now.

But I photograph everything, even the removal men packing up my house, the bees on the lavender, the market stalls, a rainy day. Besides, it's fun!