I've stayed at Honolulu's Halekulani many times over the years, and thought I knew everything about that resort. Except one thing, it turns out: Management offers guests free admission to six of Oahu's most popular attractions. It's on their website but they certainly don't tell you about it when you check in.

Other hotels around the world partner with local attractions and activities, offering free museum admission, walking tours, cultural experiences and other enticements to go out and explore. Any overnight guest can take part no matter what rate they book.

Most never take advantage, usually because they don't know the opportunities exist.

Guests staying at the Halekulani can visit the Bishop Museum, Doris Duke's Shangri-La, the Honolulu Museum of Art and the Iolani Palace as well as concerts by the Honolulu Symphony. A couple sharing a room get over $200 worth of local experiences for free.

At London's One Aldwych, the hotel invites guests on a free 90-minute tour of nearby Covent Garden with a nationally accredited "Blue Badge Guide," exclusively for those staying in the hotel. The tours operate every Saturday from July 7 to Sept. 29.

What's it worth? Were you to hire your own Blue Badge Guides, you'd pay about $235 for tours lasting up to four hours. As with the Halekulani, the hotel doesn't exactly crow about these tours. It was only after my third visit to One Aldwych that I noticed a brochure in the room offering them.

Also in London, the Bloomsbury Hotel offers guests a complimentary 70-minute walking tour of the culturally significant Bloomsbury neighborhood every Saturday morning at 11 a.m. Guests can learn about the 20 leafy squares in the area (the old stamping grounds of the literary Bloomsbury set) and visit the British Museum, led by a licensed Blue Badge guide.

San Francisco City Guides teams up with two hotels (the Omni and the Fairmont) to offer free walking tours. Both hotels are sponsors of the nonprofit City Guides tour company. Michael Cushing, City Guides' executive director, says that thanks to their financial support "we start a handful of our neighborhood tours from their lobby and they internally promote them."

In New York, the Pod hotel group, with properties in Manhattan and Brooklyn, offers daily, free walking tours led by Streetwise, a New York-based walking tour company. Monday's tours explore Little Italy and SoHo, for example, while the Thursday tour navigates Greenwich Village and the Meatpacking District. Tours leave from the hotels' lobbies and last 90 minutes. Were these tours not free, you'd pay Streetwise $200 for a group of one to four guests for tours up to four hours long.

The Triumph Hotel group in New York also teams with Streetwise. Free walking tours leave from all six properties spring through fall every day except Monday; during winter months tours depart from just three hotels on Thursday, Friday and Sunday.

In Washington, D.C., guests staying at the Jefferson can choose from three free walking tours created by the hotel's official historian, including, this summer, "A Walking Tour of DC for Hamilton Fans."

The Le Meridien hotel group offers a global program called "Unlock Art," whereby each of its more than 100 hotels partners with a cultural or artistic institution in its destination with free access (your room key is your "admission ticket"). In Paris, guests staying at Le Meridien Etoile may visit the Picasso Museum gratis, in Minneapolis it's the Walker Art Center and in Rome the Modern Art Museum welcomes Le Meridien guests. Ticket prices to these museums vary, but in most cases you'd pay from $15 to $25 were admission not on the hotel.

This is not an exhaustive list. So next time you stay in a hotel, ask if they include free walking tours, museum passes or other activities. Even if they don't, you might put a bug in their ear.