.. Where is the office, and how do I get in?

After you enter the museum, turn to your right and head for the door with notes taped on it. Those are for you.

The office door is locked. Maybe one of the notes tells you where the key is.

The note in black ink says, "Since we don't have a doormat, you'll find your key to the office with Nike."

Don't go looking for running shoes; Nike is the Greek goddess of victory, and this is a Greek art museum, after all.

Go to the group of white marble statues, and look for one of a headless woman with wings -- you may recognize it, in fact, since it's a famous image, and in case you don't, it's labeled, "Statue of Nike -- Winged Victory." The key is on the pedestal by Nike's right foot.