Lansdowne Spa -- it is nice.

I like the Mandarin, too. It is more expensive but has a lot of nice amenities. Another spa I really like is Relache at the Gaylord at National Harbor.

The Pearl in Fulton/Silver Spring. I know it is far, but it is very good, gives a great spa experience, and is less expensive than yo will find for the same quality in DC.

http://www.thepearlspa.com/

Mandarin is SO expensive. I would pick somewhere less pricey so I could get more treatments.

Bliss spa at the W Hotel DC

You should be able to do a full day at Mandarin for that- http://www.mandarinoriental.com/washington/luxury-spa/treatments/, although you can probably only do 2 treatments.
I love the Mandarin, and it is a great place to spend a full day. It has a lot of extra's- whirlpool, etc, and you get access to the infinity pool.

My 2nd choice is Lorien Spa in Alexandria. I like it a lot to, and it is cheaper than Mandarin.

i was thinking in the $600 range. I am in DC and was hoping to do it within the city, NOVA, or Moco. Thanks for the replies!

How much? The Mandarin Oriental in DC is lovely.

Salamander or Goodstone in Middleburg?

I am looking for a local place to spend a nice, relaxing day. It will be a birthday gift. Thanks in advance!