In today's visual world, a map might be the only guide you need. These Knopf MapGuides for cities come in a format small enough to fit in a purse or coat pocket, yet detailed enough to provide most of the information you need. The small fold-out maps cover the entire city and are easy to read. There is information about services, such as bank opening times. They list places to stay, shop and eat according to one's budget (the choices are good) and of course what to see. And there is a subway map in back of the book, a must if you want to get around inexpensively and efficiently.

NEW YORK

HEAR PHILHARMONIC, EXPLORE MOMA FOR FREE OR NEXT TO FREE

Time it right and you can sit in Avery Fisher Hall and listen to the New York Philharmonic for a fraction of what a ticket actually costs. Open rehearsals begin at 9:45 a.m. and end at approximately 12:30 p.m. Watch the New York Philharmonic at work, and see how a piece of music is shaped and polished by the conductor and the musicians. Tickets are $16 each and can be ordered online, by phone, by mail, by fax, or in person at the Avery Fisher Hall Box Office. http://nyphil.org/concertsTicks/.

Also, check out the Museum of Modern Art in Midtown. On Friday, tickets to that shrine to Pollock and Johns and Warhol are not $20 but ... zero dollars. Admission is free every Friday, 4-8 p.m., for Target Free Friday Nights, sponsored by Target. www.moma.org/visit/plan/offers.

IT'S LIKE WALKING ON AIR AT SEARS TOWER

Listen up, all you high-altitude thrill-seekers, The Ledge at Chicago's Sears Tower, a series of glass-floored additions that cantilever off the building's 103rd-floor Skydeck, opens early next month.

Inspiration for The Ledge came from visitors to Skydeck. "You'd only need to see the forehead prints on the windows to know that visitors are constantly trying to catch a glimpse below," Skydeck's general manager, Randy Stancik, said in a news release. On a clear day, visitors in the fully enclosed glass boxes can see four states and points 50 miles distant ... and 1,353 feet straight down.

Skidmore, Owings and Merrill, the architecture firm that designed the tower, also designed The Ledge, constructing four 1 1/2-inch-thick glass boxes on the building's west side. The retractable boxes extend 4.3 feet out from the side of the building. Each box is made of three layers of half-inch-thick glass that can hold about 5 tons, much more weight than a full group of visitors, and also greater than the two tons required by city code, according to a spokeswoman.

Admission to Skydeck is $14.95 for ages 12 and older; $10.50 for ages 3 to 11, www.theskydeck.com.