The National Gallery has seven Rembrandts and two Vermeers (and the very next day I got to see a third Vermeer across town) so you can get your quotient of Really Great Art in a few minutes. That is, unless you plonk yourself down to commune with Rembrandt himself in one of the self-portraits. I do that whenever possible -- heaven is a museum with a bench in front of your favorite painting. And I particularly love looking into the eyes of the artist himself, which happens so many times with Rembrandt; maybe he was too cheap to hire models. Here he is as a young stud, quite satisfied with himself, as he had every right to be.
Rembrandt, Self Portrait at the Age of 34, 1640
Here's his girlfriend, looking quite alluring in a bra-less fur outfit and nice jewelry.
Rembrandt, Portrait of Hendrickje Stoffels, 1654-6
Rembrandt, An Elderly Man as Saint Paul, 1659
Both the Vermeers feature a virginal, the early harpsichord popular in the late Renaissance. The instrument came in a case and was placed on a table. Apparently it didn't matter whether you stood or sat, or whether the keys were high or low relative to your body; all that technique would come later.
Vermeer, A Young Woman seated at a Virginal, ~1670-2
Vermeer, A Young Woman standing at a Virginal, ~1670-2