The tradition of most of these bastions has been to remain firmly aloof from the common folk, both Londoners and tourists. But thanks to one man's vision, the great and the good have been persuaded to get connected with each other and with the people visiting the capital for the millennium.
"The thing that's driven me on is the opportunity to reclaim the Thames for London, the hope that London might get its river back for the millennium." Dylan Hammond has had a career working behind closed doors for organisations such as Historic Royal Palaces and the Arts Council. While the Dome debate was gathering momentum, he was quietly stringing together a pearl of an idea: the simple notion that the landmarks within a 10-minute walk of the Thames should shed some vanity and loosen up.
This week, the Culture Secretary, Chris Smith, gave his blessing to the project. Thanks to Mr Hammond and the String of Pearls organisation, in 2000 you and I will be able to peer behind the scenes at the House of Lords or join a congregation of visitors to Lambeth Palace.
"I've been bowled over by the enthusiasm. What we've got is a very diverse range of Pearls, some of which see themselves in the tourism business, and others who simply want to be seen to be playing a part in national celebrations."
Some of the 50-plus gems, such as the Tower of London and Somerset House, are partially immersed in the Thames. But, for the purposes of the String of Pearls exercise, an institution does not actually have to demonstrate that it has river water lapping at its foundations. So the outstanding collections of the Imperial War Museum and National Portrait Gallery in Trafalgar both count as Pearls.
Neither does a structure have to be old. London Weekend Television's uncompromisingly 20th century cuboid is included, as is the yet-to-be- built Millennium Bridge between St Paul's and the new Tate Gallery at Bankside.
For glimpses into the past, the Public Record Office promises an exhibition of the Domesday Book, while the Royal Courts of Justice will stage re- enactments of the "Penn & Mead" trial, which established the rights of jurors.
As has happened with Open House - the Europe-wide unlocking of normally closed doors each autumn - some properties might actually acquire a taste for showing themselves off.
"Some of the Pearls are saying that if they have a good experience, they may extend the idea. Perhaps that could mean a long-term or even permanent improvement in access and what's on offer for visitors to London," says Mr Hammond.
Sadly, the one notable location that is, arguably, the mother of all pearls is not included: after a decade of dereliction, the once-mighty County Hall has fragmented into an aquarium, two hotels and a branch of McDonald's.
Maybe the new London mayor could do something about it.
You can contact String of Pearls at 1 Hobhouse Court, Suffolk Street, London SW1Y 4HH (0171-665 1540), or consult the website that was launched this week: www.stringofpearls.org.ukReuse content