Spermaceti is a substance derived from whales that was once used to make candles. This converted 1846 candle factory is now home to Nantucket's whaling history - and excursion not to be missed. It features a tremendous collection of artifacts including the skeleton of a 46-foot sperm whale, the 16-foot glass prism from Sankaty Head Light, portraits of sea captains, and a large scrimshaw collection. You can buy a separate ticket for the Whaling Museum or get a combination ticket for the other historic sites around the island. Come the holidays, the museum hosts the magical Festival of Trees. Opens daily at 10 am.