The largest and most influential islamic state impacting europe was the

The Ottoman Empire

Explanation:

A large multinational state once dominated Central Europe. The bast size of the Ottomans allowed the Islam to settle in regions like the Balkans.

In this areas the religion created communites based in Islamic teachings, for example Kosovo. Still the Islam coexisted with Christianity, in form of Orthodoxs ,Catholics and Protestants.

The end of World war meant also the end of the Ottoman Empire and soon the tensions between religion and social conflicts arose. To the present many are caution to observe the stress coming with the clash of Islam in a continent that identifies mostly as Christian.

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)