Marriott International has announced the addition of three hotels to its Autograph Collection - a portfolio of upscale, independent hotels.

The Lake Arrowhead Resort & Spa, in Southern California, and the Hotel Adagio, in San Francisco, are the first California properties added to the collection.

Lake Arrowhead, which features Spa of the Pines and a full service salon, has just undergone a US$26m (20m euro, £17m) renovation.

The third property added to the collection is The Hotel Blackhawk in Davenport, Iowa.

The hotel, built in 1910, reopened in its centenary following a multi-million renovation, and includes spa and salon Spa Luce, a heated indoor pool and whirlpool hot tub overlooking Davenport and the Mississippi River.

The Autograph Collection currently has nearly 45 properties in its portfolio but hopes to expand to 50 by year end.