On this page is a list of churches in Amsterdam, many of which can be visited.
The most important ones would be Nieuwe Kerk, Westerkerk, Oude Kerk and the Zuiderkerk. The Zuiderkerk can not be visited, but is certainly worth to have a look at.
Ice skating on Kloveniersburgwal, with view on Zuiderkerk
Old Church @ Oudekerksplein