Palamedes’ laugh was a loud bark that startled both twins. “Hah. I’m impressed. There’s not many alive today who would recognize it. This layout is based upon a design created by the great Sébastien Le Prestre de Vauban himself.”

“That sounds like a wine,” Josh murmured, still mesmerized by what he discovered.

“I met him once,” Flamel said absently. “He was a famous French military engineer.” He twisted in the seat to look out the rear window. “Just looks like junked cars to me,” he said, almost to himself.

Sophie looked curiously at her brother-how had he known that the jumble was actually a castle? But then, looking up at the walls of cars, the pattern she’d glimpsed earlier fell into place and she could see the shape of the castle, the battlements and towers, the narrow spaces where defenders could fire down onto any attackers. A shape moved behind one of the spaces and vanished.

“Over the years we’ve built up the cars like the walls of a castle,” Palamedes continued. “The medieval castle builders knew a lot about defense, and de Vauban brought all that knowledge together to create the strongest defenses in the world. Then we took the best of all styles. There are mottes and baileys, outer wards and an inner ward, a barbican, towers and keeps. The only entrance is through this single narrow alleyway, and it is designed to be easily defensible.” His huge hand moved toward the wrecked cars. “And behind and between and within the walls there are all sorts of nasty traps waiting.”

The car vibrated as it ran onto metal. The twins both slid over to the windows and looked out to discover that they’d driven onto what looked like a bridge of narrow metal pipes suspended over a thick bubbling black liquid.

“The moat,” Josh said.

“Our modern version of a moat,” the Saracen Knight agreed. “Filled with oil instead of water. It’s deeper than it looks and is lined with spikes. If anything falls in… well, let’s just say that they’re not climbing out. And of course we can set it ablaze with the flick of a switch.”

“We?” Josh asked quickly, glancing at his sister.

“We,” the knight confirmed.

“So there are others like you here?” Josh asked.

“I am not alone,” Palamedes agreed with a quick grin, teeth white against his dark face.

He drove on, past the bridge, and another alleyway curved and ended at a solid metal wall of crushed and flattened cars. It was thick with blood-colored rust. Palamedes slowed but didn’t stop. He pressed a button on the dashboard and the entire wall shuddered and silently slid to one side, leaving just enough space for the car to slip through. Once they were inside, the thick rusted gate slid silently back into position.