If you have time for only one stop in the Pasadena area, it should be the Huntington, built in the early 1900s as the home of railroad tycoon Henry E. Huntington. Henry and his wife, Arabella (who was his aunt by marriage), voraciously collected rare books and manuscripts, botanical specimens, and 18th-century British art. The institution they established became one of the most extraordinary cultural complexes in the world.

The grounds themselves are in constant renovation as the permanent collection is often relocated into other buildings to make way for new developments and upkeep. The Huntington Gallery, housed in the original 1911 Georgian mansion, is closed for renovations until 2008. Its world-famous collection of British paintings will instead be shown in the Erburu Gallery. Among the highlights are John Constable's intimate View on the Stour near Dedham and the monumental Sarah Siddons as the Tragic Muse, by Joshua Reynolds. In a too-cute pairing, Gainsborough's Blue Boy faces Pinkie, by Thomas Lawrence. Once the British paintings return to the mansion, the Erburu will be filled with American artworks. Meanwhile, in the Virginia Steele Scott Gallery of American Art you can see paintings by Mary Cassatt, Frederic Remington, and more.

The library contains more than 700,000 books and 4 million manuscripts, including such treasures as a Gutenberg Bible, the Ellesmere manuscript of Chaucer's Canterbury Tales, George Washington's genealogy in his own handwriting, scores of works by William Blake, and an unrivaled collection of early editions of Shakespeare. You'll find some of these items in the Library Hall where five tall hexagonal towers display important works. In 2006, the library acquired more than 60,000 rare books and reference volumes from the Cambridge-Massachusetts-based Bundy Library, making the Huntington the source of one of the biggest history and science collections in the world.

Although the art collections are increasingly impressive here, don't resist being lured outside into the stunning Botanical Gardens. From the main buildings, lawns and towering trees stretch out toward specialty areas. The 12-acre Desert Garden, for instance, has the world's largest group of mature cacti and other succulents, arranged by continent. Visit this garden on a cool morning or in the late afternoon or a hot midday walk may be a little too authentic. In the Japanese Garden, an arched bridge curves over a pond; the area also has stone ornaments, a Japanese house, a bonsai court, and a Zen rock garden. There are collections of azaleas and 1,500 varieties of camellias, the world's largest public collection. The 3-acre rose garden is displayed chronologically, so the development leading to today's strains of roses can be observed; on the grounds is the charming Rose Garden Tea Room, where traditional high tea is served. There are also herb, palm, and jungle gardens, plus the Shakespeare Garden, which blooms with plants mentioned in Shakespeare's works.

Opened in 2005, the Rose Hills Foundation Conservatory for Botanical Science, a child-oriented center with dozens of hands-on exhibits to illustrate plant diversity in various environments. (These rooms are quite warm and humid, especially the central rotunda, which displays rain-forest plants.) The Huntington also plans to open an ambitious classical Chinese Garden "Liu Fang Yuan" (or Garden of Flowering Fragrance) in late 2008, set to be the largest of its kind outside China. Work on this will be underway for the next several years. A 1¼-hour guided tour of the gardens is led by docents at posted times, and a free brochure with map and highlights is available in the entrance pavilion.