Bengaluru sits on the Deccan Plateau at roughly 900 metres above sea level and has no major river. Its builders worked around that by creating a chain of man-made tanks (keres) linked by channels (raja kaluves) that carried monsoon run-off from one valley to the next.
Kempegowda and his successors built or enlarged many of these tanks, including the Dharmambudhi tank, which later became the site of the Kempegowda (Majestic) bus station. In the 20th century many tanks were drained and built over. Much of the city's flooding today happens where those old valleys and channels used to run.
Surviving lakes include Ulsoor (Halasuru), Sankey, Hebbal, Bellandur, Madiwala and Agara. Lake restoration is now an important civic issue. See the News section for current coverage.