It borders the districts of Niemi in the north, Kiveriö in the northeast, Paavola and Möysä in the east, Asemantausta in the south, Hennala and Sopenkorpi in the west and Kartano in the northwest.

[1] The combined population of the statistical districts of Ydinkeskusta and Pohjoinen keskusta, approximately covering the area of Keski-Lahti, was 12,054 in 2019.

[2] Keski-Lahti has been recorded as the most dangerous district in Finland, with almost 80 homicide cases registered within 20 years.

[3][4] Upon the destruction of the village of Lahti in the fire of 19 June 1877, an initiative to create the first zoning plan for the area that would become Keski-Lahti was started.

Governor of the Häme Province Reinhold von Ammondt travelled to the derelict village on the day after the fire, and with the help of the taxman of the hundred of Hollola, K. Palmgren, took upon the planning of land acquisitions for the purpose of establishing a market town.