Address:
1200 N. Nimitz Highway
Honolulu, HI

Hours:
(closed to the public)

Directions:
From Waikiki, follow Ala Moana Blvd. toward the airport. Ala Moana turns into Nimitz, and Xerox will be on your right a few minutes after passing downtown Honolulu.

Notes:

The Old Xerox Building is a 32,600-square-foot property that houses the soundstage for indoor sets such as the Cave scenes. This property formerly housed the offices of Xerox corporation in Hawai'i, and was the site of an infamous 1999 mass murder. Afterwards, Xerox vacated the property, moving to the Kaka'ako district of Honolulu. Due to these events, the property had lain vacant until the coming of Lost five years later in 2004.

It is possible that other interior scenes and night-time Island scenes (usually with torches) were also filmed here, although this is unconfirmed.

Links:

Google Maps
Hawai'i News article on the arrival of Lost
Honolulu Advertiser article on the building of the soundstage