With more than 35,000 works of art from which to choose, deciding what to see at the Louvre can be overwhelming. Paris Muse takes the guesswork out with its six private tours. Big Picture tours are best for first-time visitors or families; they include an introduction to the museum's treasures, a Da Vinci Code-themed tour or a "Paris Muse Clues" option for kids. Closer Look tours are for more experienced museum-goers and focus on the architecture, history or hidden masterpieces at the museum.

For more information: Paris Muse

More than two million visitors flock to the Museum of Modern Art each year to see its 150,000 paintings, sculptures, drawings, prints, photographs, architectural models and drawings and design objects—not to mention 22,000 films, videos and media works. Anyone who's ever visited during peak hours knows the crowds can be difficult to navigate. But for $500, you can have the museum to yourself for an hour. Private tours are offered when MoMA is closed to the public and can be customized to focus on almost any artworks or aspect of the museum. The $500 fee is based on a group of 10, but larger or smaller groups also can be accommodated. The tours are offered in 13 languages.

For more information: MoMA

Private tours of the permanent collection and special exhibitions at the Museum of Fine Arts are available for a flat fee of $150 for one to 15 people, not including admission fees. And with the museum's Building Project, including a new 133,500-square-foot wing for Art of the Americas set to be completed in 2010, and with two revamped entrances that will open this June, there's more to see than ever.

For more information: Museum of Fine Arts, Boston

London's Tate Modern and Tate Britain offer one of the largest selections of private tours. These include customized tours for groups that might focus on a particular artist or the architecture of the museum, or take the form of a one-hour tour for two that can include a Champagne lunch or dinner or afternoon tea, all during regular museum hours. Private group tours for up to 25 people are possible when the museum is officially closed. Prices cost between $200 and $2,000.

For more information: Tate Museums

Opened in 1963, the Munch Museum has a permanent collection that includes more than 6,000 paintings, drawings and prints by Expressionist pioneer Edvard Munch. His most famous painting, The Scream, is back on display after a lengthy restoration following its theft in 2004 and recovery in 2006. Private guided tours during museum hours start at approximately $175 (plus admission fees). Private guided tours when the museum is closed include 50 minutes of general information on Munch's art and life with details on selected works, and cost an additional $400 per hour for security (plus admission fees).

For more information: Munch Museum

The 500-year-old Vatican Museums hold some of the world's most treasured art—and also some of the world's longest lines, given that the museums draw more than four million people annually. Private tours of the Vatican Museums, Sistine Chapel and Vatican Gardens are available for groups of up to 15 people for approximately $230 (plus admission fees).

For more information: Vatican Museums

With an itinerary that includes a stay at the five-star Hay-Adams Hotel, a private dinner at the original Smithsonian "Castle" building, behind-the-scenes tours of museum areas that are never open to the public, a private concert and more, the Smithsonian's 2008 Signature Event packs a lot of punch for its $2,800 price tag. Highlights include a look at the Smithsonian's usually under-wraps rare book collections, led by a book historian. "People usually don't even know that the Smithsonian has a magnificent rare book collection," says spokeswoman Amy Kotkin.

For more information: Smithsonian Journeys

The Metropolitan Museum of Art in New York City has more than two million works of art in its collection. No time to sift through all of them to find those that peak your interest? The museum's V.I.P. Tours program will customize one-hour tours for individuals starting at $400; they can also cater to groups.

For more information: The Metropolitan Museum of Art

Starting at 85 euros (approximately $135) per person, Paris Muse gives a customized experience that includes painstaking detail on highlights from prominent artists such as Monet and Cézanne. "We limit our groups to four people so that our guides can tailor the tour to the individual questions and interests of our clients," McBreen says. "In an age of cookie-cutter travel packages, that level of sophisticated, personalized attention is a luxury."

For more information: Paris Muse

The Guggenheim doesn't divide its collection of modern and contemporary art into departments by era or artist—an approach that can make for a seamless experience, but also one that might be a bit confusing for non-art experts. Get some clarity by scheduling a one-hour custom tour during museum hours for $215. If you have a group of 20 or more, you can visit while the museum is closed for a minimum of $800 per group.

For more information: Guggenheim Museum