“Now, now, Viktor!” said Karkaroff with a laugh that didn't reach his cold eyes, “don't go giving away anything else, now, or your charming friend will know exactly where to find us!”
Dumbledore smiled, his eyes twinkling. “Igor, all this secrecy, one would almost think you didn't want visitors.”
“Well, Dumbledore,” said Karkaroff, displaying his yellowing teeth to their fullest extent, “we are all protective of our private domains, are we not? Do we not jealously guard the halls of learning that have been entrusted to us? Are we not right to be proud that we alone know our school's secrets, and right to protect them?”
I don't quite understand the phrase "the halls of learning" in this context. Does it simply mean: learning something in the halls? What does it mean exactly?