Curiously enough,he open the box to find out what was in it

Curiously enough这是副词,作状语.
动词开头,可以用原形、不定式、动名词、现在分词等.
Come to school on time.祈使句
Reading is important in learning a language.动名词
Seeing from the top of the hill,we can see the whole city clearly.现在分词
To see is to believe=Seeing is believing.不定式/动名词.