The drawing above shows 1,000,000 litres of water as 33.3 tanker trucks: each icon represents 1 tanker truck (30,000 litres). It is roughly what the population of Vitoria-Gasteiz (255,000 people) drinks in two days.
In other units, 1,000,000 litres is 1,000 cubic metres or about 264,172 US gallons. Change the number in the tool or pick another reference for the drawing (glasses, bathtubs, tanker trucks, Olympic pools…) with the "Show" selector.