A must see is Convento De Cristo.  Located in Tomar, part of Santarém district, central region of Portugal.  Regardless of how many times I, you or anyone has gone there, something new is always being discovered.  There is no official tour guides, however in the summer months when local schools are off.  Knowledgeable students can guide you thru the grounds.  This is not a place you want to rush, take your time, appreciate the architecture, embrace your self in deep history.  Fruit trees thru the grounds offer some refreshment, the gardens are to be appreciated as much as the old architectural builds.