It was on the other side of the Dark Zone.
The Soothsayers had kidnapped children and put them to work digging a tunnel to escape from Gotham. One of the children, Will Thomas, escapes and fled to the Gotham City Police Department. Jim Gordon and Harvey Bullock arrived and liberated the children. Jeremiah Valeska later forced the Soothsayers into digging a tunnel into Wayne manor. He murders their leader Sykes when he objected to how hard Jeremiah was pushing his men. The Soothsayers would also be joined by more recruits, led by Jeremiah’s accomplice Ecco.
During the digging operations, Selina Kyle stabbed Jeremiah with the intent to kill him. The Soothsayers went after Selina, but she escaped with the aid of Bruce Wayne and Alfred Pennyworth. Ecco took over supervising the digging operation until they broke through and then went to wake up Jeremiah.
Later, Bruce and Alfred were forced to use the tunnels to escape an explosion that Jeremiah has triggered. Selina and Oswald Cobblepot arrive, thinking the tunnels could be used to escape Gotham, but Alfred revealed that the tunnel had led to Wayne Manor, which has been destroyed and the tunnels had been sealed.