Explore best preserved Roman temple in the world | BBC Timestamp

Now, here it is. When I first saw this building 30 years ago, I was overwhelmed. It seemed to me to be the epitome, the essence of architecture. It's the Pantheon, the best-preserved Roman temple in the world. The Pantheon was built in the 2nd century AD by Emperor Hadrian. Pantheon means all the gods. And like so many of my treasures, this building had to be worthy of divine beings. It also had to proclaim to the world that the might of Rome was unrivalled. The first thing you see as you approach the Pantheon is this huge portico with this triangular pediment. This is very much the architectural language of ancient Greece. So, here we have a Grecian element, but there's more. Each column is one great stone. It's a monolith, and these stones were brought from North Africa, from Egypt. What we see here is Hadrian bringing the culture of Greece and Egypt to Rome, absorbing it, developing it, saying, we, Rome, have conquered these ancient and great civilisations and we are the new masters of the world. But inside is a very different world, very Roman, very pioneering, very modern, especially modern nearly 2,000 years ago, because it's a vast covered space. The awe-inspiring dome is made of concrete, which the Romans invented, and remains the largest unreinforced concrete dome in the world. Having made the dome of concrete, this, the dome, then, is a rigid structure with minimal horizontal outward thrust, but it does weigh an awful lot, around 5,000 tonnes, and that has to be carried on the wall behind me. The problem is, this wall is eaten into, burrowed into by a series of these eight niches. Here's one behind me. So, how on earth does this system work? I'm now walking into the wall of the drum to see how this 5,000-tonne concrete dome is supported. Ah, what's clear is that the curved wall of the drum is not made out of solid concrete. There are these great brick arches, massively strong, and these great arches transfer the load of the dome to the solid wall each side of the great recesses, so the great dome is carried, really, by genius. The Pantheon shows the Roman Empire at its peak, flexing its muscles, showing capability and invention that Europe would not equal for nearly 1,000 years. But what did this heroic structure mean? Most intriguing, I think, is the oculus, the open space in the centre of the dome. Not just a demonstration of engineering skill to create a dome without a keystone, but it lets the light flood in, lets the sun in. The sun god, his presence is made manifest when the sun shines. The truth is, though, this great building retains its secrets. It remains mysterious and enigmatic. The Pantheon is the ancestor of every dome in the Western world. And to look at the skyline of Rome is to witness evolution in architecture.