Why do dogs always pee over where other dogs have peed?

Question

Like how Muslims build their mosques over the places of worship of other faiths?

Answer 1

Well, dogs pee over where other dogs have peed, because they want to set out their territory. It's about saying to the other dogs: this is my turf, through the scent.

As for Muslims building mosques on the places of worship of other faiths - Christians built their churches in Europe on the places of worship of the 'pagan' faiths as well. It has several advantages:
1) gets rid of the place of worship of the other faith
2) people are used to going to that place for worship and may continue doing so, even if the religion worshipped in that place is different
3) the place is already considered 'holy' by the people, so all that's needed is a transference of faith.