Lindsey Davis - Alexandria

At the Temple of Isis, I glanced in just in case the fugitive had sought sanctuary. All lay still. No parades of priests in long white robes, no sistrums sounding, no chants. An enormous statue of Isis, big-breasted and striding forwards, held a swelling sail in front of her to symbolise catching the winds for sailors' benefit. The dim, lonely interior began to unnerve me. I left.

Ahead of me rose the enclosure for the great tower. The Pharos itself had been built as a tall, slim eagerly sought landmark for sailors to aim at from far away, one clear point in an otherwise famously unmarked coastline. It was taller than other lighthouses, perhaps the tallest structure in the world – fully five hundred feet. The walls of its square enclosure were dwarfed by the Pharos within, though when I crept up to one of the long landward sides I found those walls were formed of enormous ramparts with huge gates and corner towers.

Helena had told me how the entrepreneur who organised the twelve years of building had sneakily outwitted a regulation that forbade leaving his personal mark. He had an inscription carved on the eastern walls; on a covering layer of plaster he proclaimed the customary praise for the Pharaoh: when the weather-beaten plaster ultimately peeled off, black twenty-inch letters said: Sostratus, son of Dexiphanes, the Cnidian, dedicated this to the Saviour Gods, for the seafarers. I hoped his protection would extend to me.

The Pharos was a civic building, frequented by workers who tended the fire and even by sightseers. Its entrance was occupied by only a couple of Roman soldiers. Diogenes had got past them. The guards were chatting with their boots on a table when I burst in. I introduced myself as an imperial agent, assured them I was neither drunk nor crazy, and warned them to expect trouble. One, named Tiberius, made an effort to appear alert.

'An unruly crowd is galloping here from Rhakotis. Call for backup!' I ordered. 'Send your oppo if you have to – can you communicate with the mainland?'

'We are at the world's biggest signal tower!' Tiberius commented sarcastically. 'Yes, sir. We can send a message – it anybody over there is looking in our direction, we can talk to them quite chattily… Titus! Find the torches. Signal Send reinforcements.' He sounded ready to help. Out here among the endless sea spray, any excitement was welcome. 'This will be my first riot! What's up in Rhakotis?'

'Not sure – lock up, if you can.'

'Oh I can lock up, tribune – though I'll be locking in the workers who mostly come from Rhakotis themselves.'

'Do your best.'

I limped through the gatehouse to the vast courtyards, where forty-foot-high statues of pharaohs and their queens in colossal pairs dominated the scene. Movement caught my eye: a dwarfish figure I thought was Diogenes. He was climbing the huge ramp into the main tower.

The entrance door was set a couple of storeys above ground level, for defensive reasons. A long ramp, supported on arches, led steeply up. When I myself reached the top, gasping, I found that a wooden bridge crossed from the ramp to the door. I was already feeling afraid of heights – and I had hardly started yet. The doorway was nearly forty feet high, its architraves faced in classic pink Egyptian granite. The same pink granite had been used elsewhere, an aesthetic contrast to much of the rest of the building, which was composed of titanic blocks of white, grey-veined Aswan marble.

The first tier of the building was an enormous square structure, aligned to the four quarters of the compass. Looking up, I could see it was topped by a huge decorated cornice that seemed to replicate the waves that I could hear pounding the outer walls, with massive tritons blowing their horns from each corner. This great tower tapered slightly, for stability. Above it stood a second tier, which was octagonal, and high above that, the circular fire tower, crowned with a tremendous statue. Row after row of rectangular windows must light the interior; I could not stop to count but it looked as though there might be nearly twenty floors in the first tier alone.

When I went inside I found that the interior was a vast space dominated by a central core that bore the weight of the upper storeys. There was what seemed to be accommodation for the keepers just inside the door. They resented disturbance, but unlike the soldiers they could pretend not to understand any languages I tried out. I could get no sense out of them.

I knew the basement housed stores for arms and corn. This place was vast enough to house several legions, if threatened. But currently there was no permanent garrison.

Long ramps wound up the inside walls. Up those ramps, which were wide enough for four beasts abreast, trains of donkeys toiled slowly, taking combustible materials for the light – wood, with which Egypt was poorly supplied, mighty round amphorae of oil and bales of reeds as supplementary fuel. Once they reached the top of the grand spiral, they unloaded, turned around and plodded back down again.

Nothing for it. I climbed to the top of the first, square tower. It was much the largest stage. The donkeys stopped here. Men unloaded their heavy packs and took the fuel manually up the remaining distance.

Doors led out on to a big, railed observation platform running round the exterior. Food and drink were being sold to visitors – of whom I found more than I expected. The view was staggering. On one side was the distant sweep of the city, faintly picked out by the glimmer of thousands of tiny lights. On the other, the dark emptiness of the Mediterranean, its ominous night presence confirmed by the sounds of fierce surf breaking on the rocks far below us.

Up here were lamps, men with trays, guides spouting facts and figures, and a festival atmosphere. I had never been anywhere like it that was man-made. The Lighthouse had always been a tourist attraction. Even at night, supper parties must come out here in fine weather. Rich fathers arranged birthday and wedding celebrations. Ordinary families came sightseeing, for education, fun and striking memories. There were people up here now – not throngs, but enough to make it dangerous if Diogenes had brought trouble – enough people for me to have lost sight of him and not to know either whether his two cloaked pursuers had followed him this far.

I walked around, on the way meeting Tiberius, the tough soldier from the gatehouse, together with Titus, his companion, who was carrying signal torches and what I recognised as the codebook. We failed to find Diogenes at this level, so while the soldiers cleared a space on the viewing platform and began to send their message shoreward, I left them to it, gritted my teeth and began to climb up inside the next tier.

Now I was making my way up the octagon. By the time I staggered out on to the next viewing platform, I was nearly done in. For those who wanted to make this additional climb to the top of the eight-sided tower, and who could find the stamina, a smaller balcony gave a truly spectacular view. This must be over three hundred feet above the sea. It was wonderful and horrific at the same time. Anyone here needed a head for heights that I unfortunately lacked.

Far down below in the courtyard, men swarmed like insects. On the wind came faint ululating cries. I had heard such sounds in terrible places and situations – the rebellion in Britain was the worst; remembering, I shuddered. As I leaned over, way down there on the ramp to the main door, it looked as if one scarlet blob – Tiberius? – held the riot at bay, a latter-day Horatius defending the wooden bridge. If I made it out correctly, as men from Rhakotis ran across sporadically, they were whacked and tipped off the ramp. The spectacle added to the madness of this unexpected night.