Founded in 1830, the Royal Geographical Society is the UK's group of people, British and otherwise, who share an interest in things geographical: exploration, history, you name it. They've been in their current Exhibition Road location, just south of Hyde Park, since the 1912; the original 1870s building has undergone two expansions since.
The most recent expansion, completed in 2004, was undertaken as part of the RGS's "Unlocking the Archives" initiative. The necessary funds came from the Heritage Lottery Fund, which awards funds to heritage insitutions (museums, libraries, &c.) with the stipulation that the funds go toward providing comprehensive public access. For the RGS, this access largely consists of a new reading room, wherein anyone--RGS member or no--can come to peruse and learn from the Society's holdings.
The 2 million items in the collections are all geographical in nature, as may be expected: 1 million+ maps of all dates and kinds; half a million pictures, many of which are photographs; 250,000 books (40,000 of which are circulating for Society members); nearly as many items in the archives; and 1500 artifacts. The librarian who gave our RGS tour showed us a number of really interesting items from the artifacts collection. For example, I've now seen a wash basin and pitcher from the HMS Erebus; Shackleton's balaclava from his trip on Scott's Discovery; George Mallory's climbing boot, on his foot when his body was discovered on Everest; and the hats Stanley and Livingstone were wearing when they met in Africa. Pretty darn cool.
I have to say that I like the overall mentality of the RGS library as it still pertains specifically to members. While any member of the public is welcome to utilize the collections, the majority of readers are still RGS members. These members have been used to browsing the newest publications of geographical interest, and the library still serves that need: several shelves of the few open stacks in the reading room are reserved for new publications, both popular and scholarly, which might interest a member. What a great balance between getting the masses interested while still serving the patron population!