Kaunas is located at the confluence of the two largest Lithuanian rivers, the Nemunas and the Neris, and is near the Kaunas Reservoir, the largest body of water in Lithuania.

As defined by Eurostat, the population of Kaunas functional urban area is estimated at 391,153 (as of 2023 alt=as of 2021), while according to statistics of Kaunas territorial health insurance fund there are 447,946 permanent