Finding the place was easy. Percy led them right to it, on an abandoned stretch of hillside overlooking the ruined Forum.
Getting in was easy too. Jason's gold sword cut through the padlock, and the metal gate creaked open. No mortals saw them. No alarms went off. Stone steps spiraled down into the gloom.
"I'll go first," Jason said.
"No!" Piper yelped.
Everyone turned toward her.
"Pipes, what is it?" Jason asked. "That image in the blade... you've seen it before, haven't you?"
She nodded. "I didn't know how to tell you. I saw the room down there filling with water. I saw the four of us drowning."
Alex frowned. She couldn't drown... right?
"Alex and I can't drown," Percy said, though he sounded like he was asking a question.
"Maybe the future has changed," Jason speculated. "In the image you showed us just now, there wasn't any water."
"Look," Percy said. "I'll check it out first. It's fine. Be right back."
Before Alex could object, he disappeared down the stairwell.
"Good news: no water," Percy said, when he appeared again. "Bad news: I don't see any exits down there. And, uh, weird news: well, you should see this...."
They descended cautiously. Percy took the lead, with Riptide drawn. Alex followed, her sword in her hand. She knew that if the moment came, she had to protect Piper, as she had no weapon, and Jason walked behind her, guarding their backs.
The stairwell was a cramped corkscrew of masonry, no more than six feet in diameter. Even though Percy had given the "all clear," Alex kept her eyes open for traps. With every turn of the stairs, she anticipated an ambush.
As they wound their way underground, they saw old graffiti gouged into the stones: Roman numerals, names and phrases in Italian. That meant other people had been down here more recently than the Roman Empire, but Alex wasn't reassured. If monsters were below, they'd ignore mortals, waiting for some nice juicy demigods to come along.
Finally, they reached the bottom.
Percy turned. "Watch this last step."
He jumped to the floor of the cylindrical room, which was five feet lower than the stairwell. Why would someone design a set of stairs like that? Alex had no idea. Maybe the room and the stairwell had been built during different time periods.
Alex jumped down next to Percy and offered her hand to Piper.
The room was... creepy to say the least. The curved walls had once been painted with frescoes, which were now faded to eggshell white with only flecks of color. The domed ceiling was about fifty feet above.
Around the back side of the room, opposite the stairwell, nine alcoves were carved into the wall. Each niche was about five feet off the floor and big enough for a human-sized statue, but each was empty.
The air felt cold and dry. As Percy had said, there were no other exits.
"All right." Percy raised his eyebrows. "Here's the weird part. Watch."
He stepped to the middle of the room.
Instantly, green and blue light rippled across the walls. Alex heard the sound of a fountain, but there was no water. There didn't seem to be any source of light except for their blades. If she focused, she realised she felt better, more energised- the way she felt around an ocean.
"Do you smell the ocean?" Percy asked.
Alex noticed he was right. The scent of salt water and storm was getting stronger, like a summer hurricane approaching.
"An illusion?" Piper asked. All of a sudden, Alex felt strangely thirsty.
It seemed like a place that was longing for water, that seemed strangely empty... like it was meant to hold water, but didn't have any right now.
"I don't know," Alex said. "I feel like there should be water here-lots of water. But there isn't any. What is this place?"
Jason moved to the row of niches. He touched the bottom shelf of the nearest one, which was just at his eye level. "This stone.. it's embedded with seashells. This is a nymphaeum."
Piper frowned. "A what?"
"We have one at Camp Jupiter," Jason said, "on Temple Hill. It's a shrine to the nymphs."
Piper ran her hand along the bottom of another niche. Jason was right. The alcove was studded with cowries, conches, and scallops. The seashells seemed to dance in the watery light. They were ice-cold to the touch.
Jason stepped back and examined the row of alcoves. "Shrines like this were all over the place in Ancient Rome. Rich people had them outside their villas to honor nymphs, to make sure the local water was always fresh. Some shrines were built around natural springs, but most were man-made."
"So... no actual nymphs lived here?" Piper asked hopefully.
"Not sure," Jason said. "This place where we're standing would have been a pool with a fountain. A lot of times, if the nymphaeum belonged to a demigod, he or she would invite nymphs to live there . If the spirits took up residence, that was considered good luck."
"For the owner," Percy guessed. "But it would also bind the nymphs to the new water source, which would be great if the fountain was in a nice sunny park with fresh water pumped in through the aqueducts-"
"But this place has been underground for centuries," Piper guessed.
"Dry and buried. What would happen to the nymphs?" Alex asked.
The sound of water changed to a chorus of hissing, like ghostly snakes. The rippling light shifted from sea blue and green to purple and sickly lime. Above them, the nine niches glowed. They were no longer empty.
Standing in each was a withered old woman, so dried up and brittle they reminded Alex of mummies-except mummies didn't normally move. Their eyes were dark purple, as if the clear blue water of their life source had condensed and thickened inside them. Their fine silk dresses were now tattered and faded. Their hair had once been piled in curls, arranged with jewels in the style of Roman noblewomen, but now their locks were disheveled and dry as straw. If water cannibals actually existed, Alex thought, this is what they looked like.
"What would happen to the nymphs?" said the creature in the center niche.
She was in even worse shape than the others. Her back was hunched like the handle of a pitcher. Her skeletal hands had only the thinnest papery layer of skin. On her head, a battered wreath of golden laurels glinted in her roadkill hair.
She fixed her purple eyes on Alex. "What an interesting question, my dear. Perhaps the nymphs would still be here, suffering, waiting for revenge."
Jason, Alex and Percy, formed a protective circle around Piper with their weapons drawn.
"Who are you?" Percy demanded.
The central nymph turned her head. "Ah... names. We once had names. I was Hagno, the first of the nine!"
"The nine," Jason repeated. "The nymphs of this shrine. There were always nine niches."
"Of course." Hagno bared her teeth in a vicious smile. "But we are the original nine, Jason Grace, the ones who attended the birth of your father."
Jason's sword dipped. "You mean Jupiter? You were there when he was born?"
"Zeus, we called him then," Hagno said. "Such a squealing whelp. We attended Rhea in her labor. When the baby arrived, we hid him so that his father, Kronos, would not eat him. Ah, he had lungs, that baby! It was all we could do to drown out the noise so Kronos could not find him. When Zeus grew up, we were promised eternal honours. But that was in the old country, in Greece."
The other nymphs wailed and clawed at their niches. They seemed to be trapped in them, Alex realised, as if their feet were glued to the stone along with the decorative seashells.
"When Rome rose to power, we were invited here," Hagno said. "A son of Jupiter tempted us with favours. A new home, he promised. Bigger and better! No down payment, an excellent neighbourhood. Rome will last forever."
"Forever," the others hissed.
"We gave in to temptation," Hagno said. "We left our simple wells and springs on Mount Lycaeus and moved here. For centuries, our lives were wonderful! Parties, sacrifices in our honour, new dresses and jewellery every week. All the demigods of Rome flirted with us and honoured us."
The nymphs wailed and sighed.
"But Rome did not last," Hagno snarled. "The aqueducts were diverted. Our master's villa was abandoned and torn down. We were forgotten, buried under the earth, but we could not leave. Our life sources were bound to this place. Our old master never saw fit to release us. For centuries, we have withered here in the darkness, thirsty... so thirsty."
The others clawed at their mouths.
Alex felt her own throat closing up.
"I'm sorry for you," Piper spoke up. "That must have been terrible. But we are not your enemies. If we can help you-"
"Oh, such a sweet voice!" Hagno cried. "Such beautiful features. I was once young like you. My voice was as soothing as a mountain stream. But do you know what happens to a nymph's mind when she is trapped in the dark, with nothing to feed on but hatred, nothing to drink but thoughts of violence? Yes, my dear. You can help us."
Percy raised his hand. "Uh... I'm the son of Poseidon, and this is my sister. Maybe we can summon a new water source."
"Ha!" Hagno cried, and the other eight echoed, "Ha! Ha!"
"Indeed, children of Poseidon," Hagno said. "I know your father well. Ephialtes and Otis promised you would come."
"The giants," Alex stated. "You're working for them?"
"They are our neighbours." Hagno smiled. "Their chambers lie beyond this place, where the aqueduct's water was diverted for the games. Once we have dealt with you.. once you have helped us... the twins have promised we will never suffer again."
Hagno turned to Jason. "You, child of Jupiter-for the horrible betrayal of your predecessor who brought us here, you shall pay. I know the sky god's powers. I raised him as a baby! Once, we nymphs controlled the rain above our wells and springs. When I am done with you, we will have that power again. Percy and Alexandra Jackson, children of the sea god... from you, we will take water, an endless supply of water."
"Endless?" Percy's eyes darted from one nymph to the other and then landed on Alex.
"Uh... look, I don't know about endless. But maybe we could spare a few gallons." She said awkwardly.
"And you, Piper McLean." Hagno's purple eyes glistened. "So young, so lovely, so gifted with your sweet voice. From you, we will reclaim our beauty. We have saved our last life force for this day. We are very thirsty. From you four, we shall drink!"
All nine niches glowed. The nymphs disappeared, and water poured from their alcoves-sickly dark water, like oil.