Larissa is the second largest regional unit in Greece, exceeded only byAetolia-Acarnania. It covers about one-third of Thessaly. It borders the regional units ofKozani to the northwest,Pieria to the northeast, theAegean Sea to the east,Magnesia to the southeast,Phthiotis to the south,Karditsa to the southwest andTrikala to the west.
The tallest mountain in Greece,Mount Olympus (2,917 m) is situated in the northeastern part of the regional unit.Mount Ossa is situated in the east, at the Aegean coast. The lower stretch of the riverPineios flows through theVale of Tempe, between Olympus and Ossa.
The northern part is covered withforests, but most of the regional unit is fertile land, theThessalian Plain.
Larissa has a mainlyMediterranean climate with hot summers and mild winters. Winter is harsher in the mountains areas, notably the north and Mount Olympus. Larissa is often the warmest area in Greece in summer and the coldest in winter. The highest temperature ever recorded was 45.4 °C (2000) and the coldest was -21.6 °C (1968). The city experiences very often temperatures over 40 °C.
Larissa was created as aprefecture (Greek:Νομός Λάρισας) in 1882. As a part of the2011 Kallikratis government reform, the regional unit Larissa was created out of the former prefecture Larissa. The prefecture had the same territory as the present regional unit. At the same time, the municipalities were reorganised, according to the table below.[2]
The economy increased since the annexation in 1881 and later after 1913 for the north. After theGreco-Turkish War in Asia Minor of 1920-1922, refugees were relocated to the Prefecture. Several villages were created for them across the prefecture. DuringWorld War II, the area was a major scene ofpartisan activity. The occupation and the subsequentGreek Civil War however destroyed most of the local infrastructure. From the 1950s on, the road network was significantly expanded: theGR-1 was opened in 1957 and extended in the 1960s to the Tempe Valley. In 1984, theUniversity of Thessaly opened its doors.