The original building was ordered by Agrippa, one of Emperor’s Augustus’ most trusted general and was built in 26 AD. In fact, it was the Emperor Hadrian himself who designed the building we see now and had it built almost a century later but he preserved the heritage pf Agrippa as you can read his name on top of the building. It is a temple dedicated to all the gods (Pan-Theos, which in Greek means all-the-gods). It used to be covered in shimmering marble, decorated with numerous statues and it has a huge bronze door. In 605, it was converted as a Christian Church (it still today) as Santa Maria ad Matyram. The Pantheon was stripped of most of its riches partially by order of Pope Urban VII who had the door stripped and melted the metal to make the canopy for the high altar of the Basilica of Saint-Peter, partially to make cannons for the Castel Sant'Angelo.

The first thing you notice are those huge pillars and when you get in, the dome with its center hole designed to let the light flood in is striking. As a whole, the Pantheon is just impressive in its simplicity and the purity of its lines. In it, you will find the graves of different kings (Umberto I and Vittorio-Emmanuelle II) of Italy but also the genius painter Raphael who died really young. There is also the grave of queen Margherita (after which the famous -- and patriotic -- pizza is named after).

The Pantheon one sees today is the reconstruction of a 27BC temple designed by Marcus Agrippa. It dates from 125AD (‘it’s a repro, I knew it! It looks far too new to be 27BC!’) and leaves one marvelling at the quality of its preservation. This is a complete building, heading towards 1900 years old and you can’t fail to be blown away by the architectural and engineering genius that went into its construction. Its consecration as a Catholic Church in the 7th century certainly contributed to its longevity. The bus shelter in my village isn’t one year old yet and it looks set to fall down already (mind you I wouldn’t fancy the Pantheon’s chances if our local teenagers got near it).

The Piazza della Rotunda is an extremely pleasant square with the obligatory fountain and column and well stocked with expensive pavement cafes (there is also, if you look carefully, a remarkably tasteful McDonalds directly opposite the Pantheon’s grand façade). The piazza is pedestrianised and full of people staring at the Pantheon. This ancient Roman structure demands this contemplative, open-mouthed, slightly dopey-looking preparation. The portico that fronts the rotunda is a forest of granite – three rows of eight, fourteen metre high Corinthian columns guard the doorway. Step back far enough, as you surely will trying to capture the photo, and you will see the dome rising behind the entablature. One of the first domes ever attempted, it is a hugely ambitious 43 metres in diameter and is made from progressively thinner, lighter rings of pumice-based concrete. No-one built one bigger until the 15th century. Wow.

Finally you must reunite your upper and lower jaws and enter (remembering to remove your hat – this is a church now!). Despite the inevitable crowds one’s first sensation is that of cool, open space. The interior is as high as it is wide, a great cylinder of porphyrite and granite; cool reddy browns, greys and creams make this a surprisingly simple, sober interior. Equally understated (as far as Roman tombs go anyway!) are the resting places of Raphael, the city’s Renaissance hero, and two Italian kings.

All this is lit from above as the sunlight streams through the 9m wide oculus – a circular hole in the ceiling that forms part of the supporting structure of the roof. It is also responsible for a lot of ‘oops, sorry’s’ as you wander round, staring straight up and walking into people (you can also get this really cool halo effect if you photograph someone from below with the oculus behind their head!).

Although the outside looks quite old, the interior has been restored and is quite beautiful. Even the light beaming in through the oculus (the hole in the domed roof) is interesting. In case it rains, there are four holes in the floor under the oculus so that the water can drain out. There were chairs set up in front of the alter where masses are still held.

The Pantheon is a short walk from the Trevi Fountain. Just look for the well marked signs, or follow the crowds. Like the Trevi Fountain, and so many other Roman ruins, entry into it is free and there is plenty of space so that the crowd wasn't distracting.

It does seem odd to have these ancient ruins surrounded by so many modern buildings.