I would take the metro to Friendship Heights (on the red line), and then catch the "30" buses southbound on Wisconsin Avenue. The bus goes right past the Cathedral, and there is a stop right across from the entrance. The bus is free when transferring from the metro - just be sure to pick up a bus transfer ticket at the station you get ON the metro (rather than at Friendship Heights).

Many Metro buses go right by the National Cathedral. You can get a transfer when you go into Metro rail and transfer, or depending on your starting point, just take the bus. If you want to walk, without looking at a map, I would expect the Woodley Park/Zoo stop would be closest. But it will be uphill, through a lovely neighborhood of big houses.

Another nice walk would be from Dupont Circle up Mass. Ave. through the heart of Embassy Row. You would pass the Vice President's House and the Vatican Embassy where the Pope stayed last month. Again it would be uphill. But somewhat over a mile I would judge.

"I would take the metro to Friendship Heights (on the red line), and then catch the "30" buses southbound on Wisconsin Avenue."

If you are going north, coming from downtown on Metro, I would not expect the transfer would not be valid to then go south towards where you just came from. Getting off at Dupont Circle and taking the N2 or N4 up Mass. Ave. would be the way to go, IMHO.

The nearest Metro is Cleveland Park (Red Line). Consult the station map for further directions.

Cleveland Park is an old neighborhood, where Grover Cleveland once owned a summer home - get it? Cleveland Park?

If you're very energetic walkers, you can also walk to the Cathedral from Woodley Park or Cleveland Park. Very scenic walks that I've often done myself on a nice day - you could walk west on Woodley Road or Macomb Street, for instance, which would take you through beautiful, very upscale residential areas. (Newark Street is particularly beautiful, but takes you a bit further out of the direct route.)

On a hot day, however, I would not advise this walk. In that case, I'd catch a 30s bus from Tenleytown, or a N2/N4 bus from Dupont, as others have advised.

On the cathedral grounds, don't miss the lovely Bishop's Garden and the great shops including the Herb Cottage and the Greenhouse.

And there is no need to go all the way to Friendship Heights when Tenleytown Metro Station is right there as well. I have walked from the Cathedral to Tenleytown metro station. It's pretty much flat all the way. And the 30 buses pick up from there as well. Just make sure the bus says Southern Avenue or Naylor Road and not Friendship Heights.

You can ride any of the 30-series Metrobusses on downtown Pennsylvania Avenue which go near the Cathedral, but the traffic as they inch thru Georgetown is very slow and congested all day, their times are also unreliable. You can alternatively take an N2-N4 bus starting every 10 minutes from Farragut Square going west on I street and up Mass. Ave from Dupont Circle to the Cathedral. The N2-N4s are quite fast and reliably on time, as traffic is less congested.

Thank you all so much for your advice--I'll check out the bus options. Can't wait to go!