Päijänne Water Tunnel
The purpose of the tunnel is to provide fresh water for the over one million people of the Greater Helsinki area , including the cities of Helsinki , Espoo , Vantaa , Hyvinkää , Järvenpää , Kerava , Kauniainen , Kirkkonummi , Sipoo and Tuusula . 
<triplet> Vantaa <subj> Helsinki <obj> shares border with