The Palace of Beiteddine is one of Lebanon's finest sights and makes one of the most popular day trips from Beirut. The road up through the Chouf Mountains is beautiful in itself, with sweeping views over terraced hillsides and deep valleys.
The palace was built in the early 19th century by Emir Bashir Shihab II, designed by Italian architects and constructed by local artisans. It is a sprawling complex of terraces, courtyards, small passages and richly decorated rooms. You will get pleasantly lost -- don't worry about finding your way out until you have seen the hammam (baths), the kitchens, the harem quarters, the grand reception room and the landscaped gardens.
Several museums and exhibitions occupy parts of the palace, including an Ethnographic Museum, the Joumblatt Memorial Exhibit honouring the late Druze leader Kamal Joumblatt, and an excellent collection of Byzantine mosaics displayed in the former stables.
The Beiteddine Festival, held each summer in July or August, is one of Lebanon's premier cultural events. International and regional performers play in the palace courtyard -- an extraordinary setting for a concert. Check the festival website for the current programme.
Just up the road, the curious Moussa Castle — one man's lifelong castle-building project — makes a good half-hour add-on. Beiteddine is often combined with a visit to nearby Deir el Qamar. Allow half a day for the palace alone, or a full day including the drive from Beirut and a stop in Deir el Qamar.