After leaving Tenrou Island, Alan flew swiftly southwest. Intelligence previously obtained from the Council indicated that the seven Tower of Heaven structures built by the Dark Magic Cult to use the R-System were all located in the seas around Fiore, though they only had a general radius. After learning this intelligence from Makarov, Alan and Laxus had decided to split up and clear them separately.
However, Alan knew there was actually an eighth Tower of Heaven, where Makarov's teammates Rob, Erza, and others were imprisoned. Alan wanted to rescue them before Erza's right eye was injured.
...
Chapter 53