depending on the meaning, 'przed' can be followed by instrumental case if it refers to a location of an object in front of another object or an event happening before some other event.

If 'przed' is used to describe a motion towards a front of some place, then you use accusative, e.g. 'samochód podjechał przed ratusz' - 'a car arrived in front of the city hall'.

C.f. https://en.wiktionary.org/wiki/przed