Kevin McCloud raises Tower Bridge and descends into its Victorian engine rooms, and enters a church beneath which 1500 years of London's history lie buried. In the oldest continuously working theatre in the English-speaking world, Kevin tries out a piece of stage machinery that's still operating after more than two centuries.

Kevin goes behind the scenes at Chatsworth House, and visits Castell Coch, the Marquess of Bute's Victorian gothic fantasy, complete with painted monkeys and medieval extravagance. Kevin also takes a look at the Palace of Westminster, one of the nation's treasured icons, but now badly in need of repair.

Kevin looks at six listed places where saving heritage meant a great deal of hard work from ordinary people campaigning, rebuilding, restoring and refusing to give up. The programme features a pioneering Georgian villa outside Edinburgh, Newport Transporter Bridge, a medieval timber hall, and a church saved from the Reformation.

Kevin looks at bold, modern places that challenge the idea of what heritage can be, and the places that can be the easiest to dismiss and the hardest to save. He steps inside Liverpool's Metropolitan Cathedral, which is flooded with coloured light from one of Britain's most spectacular stained-glass lanterns, and visits London Zoo's penguin pool, where the aquatic birds are treated to cutting-edge modernism.

Kevin explores places created by people who followed an obsession further than most would dare, and discovers how this singular passion can become something everyone else wants to protect. He climbs the Lovell Telescope at Jodrell Bank, and helps to repair the protected dinosaur sculptures at Crystal Palace Park that captured a Victorian idea of pre-history.