There is a particular quality to the Mediterranean light in July — not the blinding white of midday, but the amber warmth that settles over old stone walls in the hours before sunset. In Cartagena, it turns the Roman amphitheatre into something almost unbearably beautiful. The stones glow. The shadows deepen into purple. And if you are standing at the right angle, looking toward the harbour, the whole scene seems to belong to a different century entirely.

I arrived on a Tuesday, which is not the best day to arrive anywhere. The city was going about its business with the particular indifference that working port cities reserve for visitors who arrive without an obvious purpose. I had no itinerary. I had a small notebook and a vague intention to walk.

Cartagena is not a city that announces itself. Its Roman past is visible — the theatre, the forum remains, the stretch of wall near the Molinete hill — but it sits alongside a naval base, a working port, and a city centre that has been rebuilt and rebuilt again after the Civil War. The layers do not always sit comfortably together. That is, I think, part of its appeal.

I spent the first afternoon simply walking the streets between the cathedral and the harbour. The heat was serious — 36 degrees by three in the afternoon — and the streets were largely empty. A few tourists with cameras. A delivery driver arguing with someone on his phone. An elderly man reading a newspaper outside a bar, entirely unmoved by the temperature.

By six, the city had changed. The light had shifted to that amber quality I mentioned, and people had emerged from wherever they had been hiding. The terraces filled. Children appeared. The amphitheatre, which had been closed during the hottest hours, reopened, and a small group of visitors stood at the top of the seating, looking out over the city with the expression of people who have just understood something they had not expected to understand.

I stayed three days. I ate well — the local rice dishes are serious, the fish is what it should be when you are fifty metres from the sea — and I walked until my feet complained. I did not visit everything on the official heritage trail. I did not take a guided tour. I sat in the same bar on two consecutive evenings and watched the same group of men play dominoes with the focused intensity of people who have been playing dominoes together for forty years.

What I took away from Cartagena was not a list of monuments but a feeling — the feeling of a city that has been through a great deal and has not entirely made up its mind about what it wants to be next. There is something honest about that.