Ottoman period Under Ottoman rule, Grevena was a small administrative and military centre, the seat of a kaza belonging to the
Sanjak of Serfiğe within the
Vilayet of Manastir. Grevena was a mixed town and a part of its population were
Greek-speaking Muslim Vallahades. The 1920 Greek census recorded 3,108 people in Grevena, and 200 inhabitants (40 families) were Muslim in 1923. Due to its small size, the town's Ottoman past, represented through a few public buildings and the homes of Muslims located in the urban centre, all disappeared during the 20th century. Another mosque existed in Grevena and was converted into a church in 1927; later it and its minaret were demolished, and the church of Agios Achillios built on the site. Military barracks remained until World War Two, and were later destroyed.
1995 earthquake The earthquake that occurred in the region on 13 May 1995 was 6.6 on the
Richter magnitude scale, but it caused only material damage. The worst hit area was the county of Ventzia. There were two foreshocks of lesser intensity that preceded the main earthquake by a few minutes and warned people. These warnings sent the population out of their houses. When the main earthquake came, it destroyed nearly all the houses in several villages of the Ventzia County – the houses collapsed to the ground – but all the inhabitants were outside. Another earthquake on 5 January 2005 measured 4.9 near Grevena. It took place at 20:00 local time (EET), and no damage was reported. Another earthquake with a measured intensity of 5.4 occurred on 17 July 2007 at 21:23 local time (EET) and was followed by weak aftershocks. Some older buildings were lightly damaged in villages northeast of Grevena. ==Administrative division==