The geographical feature that is a natural lake formed by volcanic activity is a crater lake. These lakes occur in volcanic craters, resulting from the collapse of a volcano or the accumulation of water in the basin left after an eruption. Notable examples include Crater Lake in Oregon, USA, which is known for its deep blue water and stunning visual clarity. Crater lakes often support unique ecosystems and can be important ecological and recreational sites, drawing visitors fascinated by their beauty and geological history.