Pechanga Resort & Casino in Temecula, California, is in the final phase of a US$285m (€240m, £212m) expansion which will see it become the largest casino resort in the state.

The work on the resort – which is owned by the Pechanga Band of Luiseño native Americans – includes a new hotel tower, which will increase the number of rooms at the property to 1,090.

At the centre of the expansion is a new, two-storey luxury spa. Featuring 17 treatment rooms, facilities at the 25,000sq ft (2,320sq m) Spa Pechanga will include a wet area with steamroom, sauna, private pool with cabana massage services, spa pool and two indoor hydrotherapy pools.

There will also be a large health and fitness club and and a full-service nail and hair salon.

The spa menu will feature a range of massages, facials, body scrubs and skin treatments, with suppliers including French-based product house GM Collin.

Signature treatments will feature plants and flowers considered integral to healing by Pechanga tribal members.

“This development will build upon the quality and reputation of the original resort and continue our Tribe’s entrepreneurial spirit for future generations,” said Mark Macarro, tribal chair.

The Pechanga Resort & Casino first opened in 2002 and was designed – by Delawie architects – to highlight the Pechanga Band of Luiseño Indians' culture.

Delawie has also designed the new expansion, with Lifescapes International acting as the pool and landscape architects.

The expansion will have its official opening on 22 December.