Honorius reached below his desk and produced a map of the water system, an enormous scroll formed of many different sections of parchment. He unrolled it and weighted it down with short sections of worn lead pipe.
‘See here.’ A plump finger indicated a point in the centre of the map. ‘The castle is one of the thirty-five supplied by the Old Anio, which takes its waters from the Tiber above the twentieth milestone and enters the city close to the Viminal Gate.’ Like every Roman, Valerius knew that the Old Anio, as opposed to the New Anio, was notorious for the poor quality of its waters, known universally as rat’s piss and of similar colour and taste, but Honorius insisted on elaborating. ‘Only six per cent of the supply will ever reach an imperial building, and that for the latrines. Most is used for industry or irrigation. The rest ends up in the Subura, where they are less inclined to complain about a little cloudiness.’
Mention of Subura reminded Valerius that the warren of streets overlooked by the Quirinal, Esquiline and Viminal hills provided a perfect refuge for a secretive cult like the Christians. It was here Petrus had set up his herb shop and surgery, and close by that they had stumbled upon the young man preaching at the crossroads. He noticed Honorius frowning.
‘Now that I consider it,’ the water commissioner mused, ‘this would be the perfect supply to tap if one needed any great quantity. We treat Old Anio with a little less respect than we give to the other aqueducts, precisely because of the quality of the water and whom it supplies.’ He shook his shaggy head. ‘Regrettable, but understandable. It may be that the engineer I sent to investigate this leak did not treat it quite as diligently as he would if he had been inspecting the Virgo or the Aqua Claudia.’ He let out an unlikely chuckle and Valerius recognized the enthusiasm of a true professional. ‘Perhaps it is worth taking a second look?’
Honorius summoned a work detail and they set off for the Cespian Height. Their route took them through the bustling heart of the Subura, but Honorius was a magistrate whose rank warranted the accompaniment of six lictors and their progress was swift as the crowds parted before the heavy ash rods of the bodyguard. As they walked, with the lictors at their head and the water gang behind, Valerius studied the narrow streets and wondered if he was wasting precious time. Was it really possible to find one man in all of this? Twenty minutes later they reached the base of the slope and it took another five to climb to the water castle. In scale, though not in splendour, the castle resembled its religious neighbour. This was clearly a working building, massive and brick-built, perhaps forty feet in height and forty paces long, supplied from the north by a main spur of the Anio.
The water commissioner came to a halt in the shade of the tower and instructed his men to check the exterior for leaks or signs of theft. ‘By the by,’ he turned to Valerius, ‘you must pass on my congratulations to your father.’ He waited for a reaction, but none was forthcoming. ‘Bassus the geologist mentioned it only yesterday. Strictest confidence, of course. Surely he must have told you?’
Valerius nodded distractedly, wondering what the old man was talking about. Honorius shrugged and returned to the matter of the tower. ‘You see,’ he explained, ‘how it supplies four main channels and numerous smaller ones.’ He called for a ladder as Valerius studied the stone conduits and lead pipes. ‘I do not normally do this these days, young man, but needs must and truth be told your little mystery quite invigorates me. I haven’t had so much excitement since the Marcia collapsed during the consulship of Hosidius Geta.’ He hauled his substantial bulk up the ladder, puffing noisily and resting every three steps, while Valerius hung on behind him with his good hand and tried not to look upwards. A gentle breeze ruffled the tree tops and from his perch Valerius noticed a hawk arc across the city seeking out some sleepy pigeon or sparrow. From this height they had an unsurpassed view across the shimmering rooftops to the marbled glory of the Forum and the columned temples of the Capitoline. The heart of Rome, laid out like some child’s toy or commander’s sand model. Valerius was reminded of the wooden table he had seen in Nero’s palace and he wondered again at its purpose. Did the Emperor look upon the cityscape as Valerius did now and glory in its colour and diversity and magnificence? Or were its people only so many ants striving to supply his imperial coffers? Doubtless both, knowing Nero’s capricious nature, plus a ruler’s paranoia that below each roof lay a potential enemy. Honorius reached a narrow terrace running around the castle and clambered awkwardly on to it over the low wall. Valerius joined him in front of a wooden doorway set into the brick. The water commissioner searched in a leather pouch at his waist and came out with a large key. ‘Good.’ He frowned absently. ‘It wouldn’t be the first time I’d forgotten you.’
The key turned easily in the lock and the door opened with only the barest squeak. Honorius ducked his head and ushered Valerius into the cool of the interior, where the rush of water echoing from the stone walls instantly assaulted his ears. Barred windows set high in the walls provided enough gloomy light to allow them to see each other, and as his eyes adjusted Valerius was able to make out the inside of the building. They stood on a walkway which encompassed three sides of a massive tank of dark, swirling water supplied by a foaming torrent at the far end. The constant movement and a sensation that something was about to emerge from the bottomless depths and swallow him made Valerius instinctively step back and make the sign against evil. Honorius saw his reaction and grinned.
‘It affects people like that the first time,’ he roared above the noise of the water. ‘But don’t worry, we don’t lose many.’
Still shouting, Honorius pointed to the wall and Valerius caught the shine of metal. He made out a number of strange levers of different sizes. ‘The smaller levers operate the opening and closing of separate pipes, the larger, the outlets for baths and factories and the imperial gardens. It is a simple system involving pulleys and axles. In theory, the leakage could come from any of these pipes; in practice it is most likely to come from the outlets with the biggest capacity.’
‘So the leakage doesn’t come from this castle?’ Valerius found himself shouting even louder than Honorius.
‘Not from the castle itself, but certainly from this system. We have measured the flow above and below the tower and the supply is down by as much as a tenth. I have the men checking each of the four major channels.’
‘Four?’
‘What?’
Valerius took the older man by the arm and led him through the door into sunlight and relative quiet. ‘You said four channels?’
‘No need to shout, young man. That is correct.’
Valerius walked around the terrace, leaning out to study the exterior of the castle and the channels running from it. ‘I believe I count five large outlets.’
Honorius glared, annoyed at the attempt to contradict him. ‘Yes, but the fifth is no longer in use. It is the conduit which once supplied the Glabrian baths. See,’ he pointed through the door, ‘the opening mechanism has been removed. The line has been dry for years.’
Valerius was Roman born and bred but he had never heard of the Thermae Glabrianae.
‘They were built, I believe, in the consulate of Marcus Acilius Glabro, more than two hundred years ago,’ Honorius explained in his dry voice. ‘But they were demolished in the time of Augustus. The family hadn’t had the money to maintain them for years. The land was handed to the state which naturally sold it to some unscrupulous property developer for housing.’
‘What land?’