Dumbarton Oaks is really at least four things, and arguably more. That is both its strength and its primary drawback from the standpoint of a visitor.
The house itself was the gift of Robert and Mildred Bliss to Harvard University, along with their art collections. Because this was the Bliss's home and because of their tastes in collecting as well as diplomatic accomplishments, the house itself has several parts.
The first, and probably the primary attraction for most visitors, are the extensive gardens, which may come as a surprise to one visiting Washington, DC. According to the website, the garden has been ranked as one of the best in the world. You will want to book ahead for the garden as they only have timed tickets. The cost was a little less than $15.
We liked the gardens, but they felt a little unkempt compared to others we have seen in the US and Canada. Still, they are very nice and fun to walk around.
The second attraction is the museum inside, which is free, and based on the Bliss's own collection. This really has two main parts, a collection of Byzantine Art and one of pre-Columbian art from South America. This second collection is in a well-designed and architecturally interesting addition. The works and their descriptions are all excellent. The Byzantine works had their own interest, but we did not find them as striking. The main house also has a library that is largely roped off, so it is of lesser interest.
There are no guides, or at least there were none during our visit, only security guards.
One feature of the main house is the impressive music room. Unfortunately, the descriptive materials were not that good. One painting on the wall was plainly an El Greco, but the descriptions said little about it. The piano had signed photos by Igor Stravinsky, who must have been a friend but, again, no description and I simply recognized it from photos of Stravinsky elsewhere. They had other autographed photos from musicians or composers, but it was too dim to make out the signatures.
This room is also where meetings were held in 1944 leading up to the formation of the United Nations. I only knew that because we visited with a political science commentator. There was virtually nothing about it. It's still a great room, but it might be worth reading ahead.
And that takes us to what this site needs, which is a dedicated curator who wants to show visitors all of these disparate parts and possibly even tie them together. What is in the roped-off library? There are several empty displays along the way - surely something in the museum could go there. The Blisses donated the property to Harvard in 1940 and perhaps it is not a priority for a university several hundred miles away. Still, this otherwise wonderful site and its visitors deserve a little more.
The moral: Read up, come, and enjoy.