We often use libraries as a resource while traveling. Almost every town has one, they offer free WiFi, and are quiet, air-conditioned places to spend some time.

On road trips, we'll use them as rest stops. We seek out the familiar blue-and-white sign with the icon of a figure reading a book to point the way to the local library. We know we'll find clean restrooms and a place to relax, along with a used-book rack that offers plenty of choices at bargain prices.

In large cities, many public libraries are overlooked free attractions in their own right, providing noteworthy architecture and rotating exhibits. A few examples:

The Boston Public Library offers free art and architecture tours of its Charles McKim-designed building and art collection. A massive gallery decorated with murals by John Singer Sargent stacks up against many museums.

The New York Public Library, on 42d Street, hosts a changing selection of professionally curated exhibits: the current one, "Printing Women: Three Centuries of Female Printmakers, 1570-1900," runs through Jan. 31.

The Free Library of Philadelphia's Rare Book Department is hosting "Sacred Stories: The World's Religious Traditions" through January. Religious texts dating to medieval times are on display, including Martin Luther's first German New Testament, printed in 1522.

The Albert Balch Autograph Collection at the Seattle Public Library boasts more than 8,000 items signed by notables from W.E.B. Du Bois to Babe Ruth.

The Egyptian Revival-style Los Angeles Central Library is decorated with wonderful murals, along with samples from its vintage travel poster collection, a must-see for anyone who dreams of far-away places.

Before visiting a city, do some research on the main library to find these hidden gems. Large public libraries also have gift shops with literary souvenirs not found elsewhere, some of which are tied into their current exhibits.

Larissa and Michael Milne are the authors of the historical travel guide "Philadelphia Liberty Trail," which, they are happy to say, is available at all the libraries noted above.