英语听力：自然百科 圣保罗大教堂（在线收听）

For nearly 300 years, the dome of the present St. Paul’s Cathedral has presided over London's skyline. Considered one of England’s most beautiful landmarks, two designs by noted architect Sir Christopher Wren were rejected at first. But revised plans were accepted in 1675.

"Wren had one great idea, and that was to have a great domed building. That was the one thing that was essential to his concept of the cathedral from beginning to end. It proved to be too revolutionary, I think for the dean and chapter of the time. It was too much a single domed building not sufficiently a building that had nave, chancel, choir, aisles. "

Wren redesigned and persevered for nearly 50 years, living to see the dome’s construction completed. Weighing more than 71,000 tons when finished, it was a logistical and engineering feat.

Inside, the cathedral combines architectural splendor with historic memorials. The tombs of British military heroes, the Duke of Wellington and Admiral Horatio Nelson are situated near American military heroes, in a chapel commemorating US service men and women who died during World War II.

Now the cathedral is undergoing its most extensive restoration to date. Parts like the dome were repaired decades before, but items like the peristyle just below needed some attention this time around. The weight of the dome pushed out the supporting wall, causing it to crack.

"While the stones are pushed displaced, they open up and the water can then get in through the skin of the building. Now Wren used a certain amount of iron work.If iron gets wet as we all know, it rusts. When it rusts, it expands. When it expands, it blows the stonework to pieces. It’s therefore extremely important that we keep the whole thing watertight."

Water also seeps through stone into an iron belt that supports the dome, destroying the surrounding stone.

What you are actually seeing here is one of the lower fractures that come right down through the chain. We’re just making sure that the chain is whole, protected and doing its job.

The Portland stone blocks replacing those damages in the peristyle are hand-carved, just as they were three centuries ago. But interior walls were gently cleaned, using 21 century mixtures of rubber latex and alkaline base. Combining tradition and technology in this restoration project will allow millions to enjoy the cathedral for centuries to come.

The dean and chapter: The legal corporation and governing body of a cathedral. It consists of the dean, who is chief, and  his canon or prebendaries.