ios ▁Valley ▁to ▁the ▁south . ▁Th ess aly ▁is ▁a ▁ge ograph ically ▁diverse ▁region , ▁consisting ▁of ▁broad ▁central ▁pla ins ▁surrounded ▁by ▁mountains . ▁The ▁pla ins ▁are ▁bounded ▁by ▁the ▁P ind os ▁Mountains ▁to ▁the ▁west , ▁Mount ▁O th rys ▁to ▁the ▁south , ▁the ▁Pel ion ▁and ▁O ss a ▁ranges ▁to ▁the ▁east , ▁and ▁Mount ▁O ly m pos ▁to ▁the ▁North . ▁The ▁central ▁pla ins ▁consist ▁of ▁two ▁bas ins , ▁the ▁Lar isa ▁bas in ▁and ▁the ▁K ard its a ▁bas in , ▁dra ined ▁by ▁the ▁P ine ios ▁River ▁into ▁the ▁V ale ▁of ▁Tem pe . ▁The ▁P agas etic ▁G ulf ▁in ▁sout he astern ▁Th ess aly ▁was ▁and ▁is ▁the ▁only ▁body ▁of ▁water ▁suitable ▁for ▁har b ours ▁in ▁region . ▁▁ ▁Str ict ly ▁speaking , ▁Th ess aly ▁refers ▁primarily ▁to ▁the ▁central ▁pla ins ▁inhab ited ▁by ▁the ▁Th ess ali ans ▁in ▁anti qu ity . ▁The ▁pla ins ▁were ▁divided ▁in ▁anti qu ity ▁into ▁four ▁administrative ▁regions ▁called ▁t et rad s : ▁Pel as gi ot is , ▁Ph th iot is , ▁Th ess ali ot is , ▁and ▁Hist iae ot is . ▁In ▁its ▁bro ader ▁sense , ▁Th ess aly ▁also ▁included ▁the ▁surrounding ▁regions ▁called ▁the ▁per io ik oi , ▁which ▁were ▁regions ▁inhab ited ▁by ▁different ▁eth nic ▁groups ▁that ▁were ▁closely ▁tied ▁to ▁the ▁Th ess ali ans