The National Archives of Scotland are still housed in the same building purpose-built in 1780 for storing and providing access to registers and other historical records. Actually, 1/3 of the NAS is still housed in this building; another 1/3 is located down the street in another period building, while the final 1/3 is housed in a modern purpose-built facility, complete with up-to-date storage and conservation studio.
Why might a national archive for a place the size of Scotland need to occupy three whole huge buildings? Well, the NAS is actually split into 8 total departments, each specialized in a particular type of research that can be conducted via the archive records. Do you want to track down court records of any old court case? There's a division for that. Same goes for things like tracking down Scottish wills, records of the Kirk, and family history.
Tracing one's family history, in fact, has become quite the popular pursuit as of late. The NAS had so many visitors with this particular goal that, following recent renovations, a large portion of the main building across from the Balmoral Hotel on Princes Street is now dedicated to ScotlandsPeople, an entirely computer-based series of readings rooms and records that can allow visitors to track down their lineages. According to one of the librarians who spoke during our visit, between 80 and 90% of all reference enquiries pertain to family history. The NAS was quite smart, in my opinion, to take steps to really satisfy those archives users.
Despite housing some really historical records (70 kilometres of records, to be exact, spanning from the 12th century to the present day), the NAS is also very much keeping things modern and as accessible as possible. They have a fully searchable OPAC that users can search on- and off-site, and they are taking on some really substantial digitisation efforts. One such "Virtual Volume," as the NAS calls them, is a complete digital record of Scottish wills from 1500-1901. Because the wills themselves are so fragile, now that they are digitised (of a very high quality, from what I saw), readers can view and even take home a copy without any threat to the original, which will be preserved for posterity. The NAS also has an initiative to digitise all of its Church of Scotland records. Again, these records will be more easily available without having to worry about document preservation concerns in the reading room.
All grand efforts to satistfy the twofold mission of the NAS: to preserve, protect, and promote their national records; and to make them accessible to educate, inform, and engage readers.