How does water travel up to our pipes if we live in a very high Apartment/work in an Office?

In Melbourne, Australia we have the Eureka Tower and Realto tower. How do water travel up to the highest floor?

They use hydraulic pump in water network to pump water from ground to the tank on the top of the building . Normally the pump works at night because at night, water pressure is higher .

They use water pumps.

http://en.wikipedia.org/wiki/Pump

by hydraulic pump or summer severs