Houses of Parliament & Big Ben (Elizabeth Tower)

Formally the Palace of Westminster, this riverside complex has been the seat of English and then British government since a medieval royal palace first stood on the site, though almost everything visible today dates from after a catastrophic fire gutted the old buildings in 1834. Only Westminster Hall, with its extraordinary medieval hammerbeam roof, survived the blaze largely intact and still stands at the heart of the complex.

The rebuild, led by architect Charles Barry with Augustus Pugin responsible for its lavish Gothic Revival detailing inside and out, took over thirty years to complete and produced one of the most recognisable skylines in the world. UNESCO has since listed the Palace of Westminster, together with the neighbouring Westminster Abbey and St Margaret's Church, as a World Heritage Site.

Chief among the palace's towers is the Elizabeth Tower, officially renamed in 2012 to mark the Queen's Diamond Jubilee, but known to almost everyone by the name of the Great Bell hanging inside it: Big Ben. Strictly speaking, Big Ben refers only to that bell, not the tower or its clock, but the nickname has been applied so consistently, for so long, that correcting people has become something of a lost cause.

The clock's famous accuracy is maintained by a wonderfully low-tech method: old pre-decimal penny coins are added to or removed from the pendulum's tray to fine-tune its swing, since even the tiny added weight of a single coin shifts the timing by a fraction of a second a day. Inside, the Commons and Lords chambers still debate the business of the nation beneath vaulted ceilings and stained glass, making this one of the very few historic monuments in the world that is also a fully functioning legislature.

Guided public tours do not run every day: they're offered only on Saturdays and during parliamentary recess periods, so this is one attraction that genuinely needs to be planned around a specific calendar rather than dropped into a walking route. Tickets can sell out well ahead of time in peak season, so it's worth booking online as early as possible.

UK residents have an alternative route in: it's possible to arrange a free tour through your local Member of Parliament, which is worth investigating if you live in the UK and want to visit outside the usual paid tour windows.