Castle Hotel & Spa is set to open a US$9m (7m euro, £5.6m) Thann Sanctuary Spa in Westchester County, New York, US in May 2013.

The 100-year-old resort, overlooking the Hudson River in Tarrytown, is owned and managed by Sankara Hospitality Group.

Spanning 7,800sq ft (725sq m), the spa will be the first Thann Sanctuary-branded site to launch in the US.

It will feature seven treatment rooms, hot pools, men and women's separate steamrooms, and a VIP treatment suite.

Thann Sanctuary Spas operates a number of spas across Asia and is based on a holistic treatment approach that aims to rediscover inner physical and mental wellness.

Treatments include ayurvedic body massages, energy healing therapies and Nano Shiso anti-aging facials.

The 90-minute signature massage at the Thann Sanctuary at Castle Hotel will involve deep tissue treatment, incorporating firm palm and forearm pressure to heal muscular aches and pains.

The interior design, which is being carried out by US design firm Gettys, will include warm tones and soothing light with furnishings procured from Thailand.

California-based KTGY is responsible for the architectural design which will focus on achieving a simple, sophisticated building using stone walls and minimal exterior openings to blend with its setting.

A curved stonewall will guide the guest through an opening in the wall into a sheltered interior courtyard.

The spa will have a strong focus on sustainability and will be LEED-certified by the US Green Building Council.

Jiro Sato, president of Sankara Hospitality Group said the development of the spa is the first phase of a ten-million dollar renovation project.

"Renovations will also be carried out on 4,100 sq ft (381 sq m) of meeting & banquet space, the 31 luxurious guest rooms and suites, public spaces, and the award-winning Equus restaurant and kitchen. The luxurious space will open in May 2013 and will be a magnificent addition to Castle Hotel & Spa."

Originally built in 1897 as a private residence, the Castle Hotel & Spa opened in 1997, 16 years after it was designated a historic landmark.