Churches have steeples pointing to heaven. Take away any signs from in front of the building, and you still know it’s a church; you just don’t know, for certain, the denomination.
Courthouses often have a cupola of some sort atop their roof, with a clock announcing to passers-by the time to draw near and be heard. Without a sign, they might be confused with a library – not a far reach from their purpose as a repository of important information – but never would they be mistaken for, say, an entertainment center.