HOMS, Syria (AP) — With a gigantic explosion, Syrian rebels on Thursday leveled a historic hotel being used as an army base in the northern city of Aleppo by detonating bomb-packed tunnels beneath it, activists and militants said.

The blast near Aleppo’s medieval citadel, an imposing city landmark that was once swarming with tourists, killed an unknown number of soldiers. It turned the Carlton Hotel, known for its elegant architecture and proximity to the citadel, into a pile of rubble.