Translation:The museum's entrance is large and closed.
I would say "the museum's entrance" to make it clear that I'm talking about a certain museum. That's also a possessive structure that matches the structure used in the Hungarian sentence. "The museum entrance" is more similar to a compound noun, like múzeumbejárat. But I just might be nitpicky. I do see your point, and in actual usage the difference wouldn't matter much.
Ray, in principle there's nothing wrong with your translation, but note how you introduced a second clause through the addition of a comma and another conjugated verb "is". The Hungarian sentence only has one clause. To match your English translation precisely, the Hungarian sentence would have a comma before és.