The standard against which all omnibus museums have been measured ever since it opened in 1753, the British Museum is undoubtedly worth a trip to London in itself. Personally, I don't consider any sojourn to the British capital worthy of the title without poking my head in here – however briefly – and you could happily spend years inside without scratching the surface of its collections. Unfortunately, time is brief, and with 15,000 visitors a day seeking to do the same, it's important to plan your visit (or visits) strategically:
Plan! The British Museum is immense, and even a cursory stroll through the galleries takes a day. Consequently, decide beforehand what you absolutely must see – perhaps choosing its highlights or deciding to focus on a particular collection. Remember that it's not so much one museum as many all organized according to the same principles of completeness and curation by specialist scholars. Be sure to pick up a free map and note that while the "classical tour" is expensive, the volunteer-run Eye-opener Tours covering individual sections of the museum are free.
Visit the most popular sections on a weekday afternoon or weekend morning: School groups tend to visit during the morning on weekdays, while weekend afternoons tend to be busier than the mornings and most people head for the highlights – the Egyptian, Greek, Roman, and Near Eastern collections are the most popular. In general, the large tours avoid the side galleries, so if you're stuck in a crowd, these rooms (which tend to also have the more informative labeling) are the best respites within these collections. The new Sainsbury Africa Galleries and Asian Collections are only slightly less impressive (and heavily visited.)
At peak times, head for less famous collections: Although they can't match Mediterranean treasures, such as the Elgin Marbles and Rosetta Stone (nothing can really!), the museum's little-visited Islamic collection is one of the best of their kind in the west, and its soaring displays of Native American life quite interestingly fuse modern and pre-Columbian artifacts. The museum's most underrated permanent exhibition is the new Enlightenment Gallery housed in the King's Library, which provides a sense of the intellectual undercurrents behind the museum's creation (its collections also spawned what are now the British Library and Natural History Museum) and how it originally looked.
Don't forget to appreciate where you are. Without its collections, the British Museum's buildings, in the historic intellectual quarter of Bloomsbury, would be intriguing in their own right as paragons of 19th-century architecture. The present quadrangular outer building, designed by Sir Robert Smirke, was completed in 1852 and has been significantly expanded since. The round Reading Room in its central courtyard, by his brother Sidney, was completed in 1857. After the British Library was established in 1998, the courtyard was covered over by Lord Norman Foster to form Europe's largest public square. It's perhaps the most attractive juxtaposition of historical and contemporary architecture in a city full of such combinations.
http://www.thebritishmuseum.ac.uk