Where – and when?

The Byzantine Empire lasted for more than 11 centuries, from AD330-1453. At various times, it incorporated most of Europe, including the Balkans, and Turkey, parts of North Africa, and the Middle East. Predominantly Greek-speaking and Christian, its power superseded that of the Roman Empire. The imperial capital was Constantinople, formerly Byzantium, today Istanbul, a city that wielded considerable power until it was eventually conquered by the Ottoman Turks.

Some 300 of the greatest treasures of the Byzantine Empire are currently on display at the Royal Academy of Arts in London (Burlington House, Piccadilly; 020-7300 8000; royalacademy.org.uk), in an exhibition put together in collaboration with the Benaki Museum in Athens. Among the treasures are the "Antioch Chalice", on loan from the Metropolitan Museum of Art in New York, once thought to be the Holy Grail; and nine icons from St Catherine's Monastery in Sinai, which have left Egypt for the first time.

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The exhibition continues until 22 March, and several free lunchtime lectures on different aspects of Byzantium will take place between now and then. The Royal Academy opens 10am-6pm daily, until 10pm on Fridays. Admission to the exhibition costs £12. Timed tickets can be booked in advance online or by phone (0870 848 8484) and cost £13.50.

What can I see of Byzantium today?

Like the Roman Empire, Byzantium left an indelible mark on its lands. If you have travelled at all, you are likely to have seen the influence, if not the actual cities, of Byzantium. Byzantine architecture, typified by a Greek cross plan, or later the cross-in-square design, can be seen in churches such as St Sofia, in the Bulgarian capital Sofia; the monastery of Djivari in Georgia; and the cathedral in Kiev. In other buildings, most notably the Dome of the Rock in Jerusalem, Byzantine craftsmen were used to create the mosaic decoration. And Byzantine artefacts have found their way into collections as varied as that of the National Museum in Belgrade and the Cathedral Treasury in Troyes, France.

Where to start?

Istanbul. Most of what was Constantinople is contained within a triangular peninsula south of the Golden Horn; much of it is still enclosed within the old Byzantine walls. The aim of the Emperor Constantine was to create a city that would outdo Rome, and he constructed a number of public buildings to add to its grandeur.

British Airways (0844 493 0787; ba.com) and Turkish Airlines (0844 800 66 66; thy.com) both fly to Istanbul's Ataturk airport from Heathrow; Turkish Airlines also flies there from Manchester and Stansted, and, from 15 December, will operate five flights a week from Birmingham. And easyJet (0905 821 0905; easyjet.com) flies from Gatwick and Luton to Sabiha Gokcen airport, 20 miles south-east of the city, on the Asian side of the Bosphorus strait.

These days, a certain amount of imagination is required to visualise the layout of the imperial city. The Forum, known as the Augusteion, was on the space that is now Sultanahmet Square; along one side were the Aya Sofya baths, now the Turkish Handwoven Carpet Sales Centre (00 90 212 638 0035). Even if you don't need a carpet, it's worth a visit to see the architecture.

Across the square from the baths is the Hippodrome, the construction of which was started by the Romans, but finished and expanded by the Byzantine emperors until it was considerably larger than its modern remains suggest. The pillars we see today were part of a line of columns representing the Axis of the Empire and symbolising its power.

Close by is the Byzantium Hotel, at Akbiyik Caddesi 29 (00 90 212 458 6200; thebyzantiumhotel.com), a pleasant boutique property in the heart of the old quarter. A double room costs €90 (£75), including breakfast.

The Byzantine city was dominated by the Emperors' Palace, much of which is now buried beneath the modern city. Excavations near the Blue Mosque revealed Byzantine mosaic floors dating from the 6th century, and these are now displayed, in situ, in the Mosaic Museum, or Buyuk Saray Mazikleri Muzesi, on Torun Sokak (00 90 212 518 1205).

But Istanbul's finest Byzantine monument is the church of Aya Sofya. Constantine wanted to build a Christian city, and he had a basilica constructed opposite the Forum. This was rebuilt some 200 years later by Justinian, who commissioned Aya Sofya, Constantinople's most impressive monument and one of the greatest buildings in the Christian world, smaller but a thousand years older than St Peter's in Rome. The basilica is now a museum (00 90 212 522 1750), open 9am-5pm except Monday.

Before he commissioned this masterpiece, Justinian had a trial run, and had the church now known as Little, or Kucuk, Aya Sofya built on Kucuk Aya Sofya Cad. Now converted into a mosque, this square structure, with pillars inside supporting a dome, was modelled on the church of St Vitale in the Italian city of Ravenna.

Is this a place I should visit?

Yes, and Ravenna is easily accessible from several of the cities on the Ryanair network (0871 246 0000; ryanair.com), including Rimini (from Stansted and East Midlands); Bologna (from Stansted, Birmingham and Edinburgh); and Ancona (from Stansted).

Ravenna, which had been an important city of the Roman Empire, was developed under the Byzantines to become the greatest artistic centre in Italy, and capital of the Western Empire. The Byzantines maintained and developed the tradition of mosaics, elaborate pictures made of pieces of hard stone, or tesserae, which were irregularly cut and then glazed so that they would glitter in the light.

Many of the monuments in Ravenna are decorated with mosaics, and the best are considered to be among the masterpieces of Byzantine art. The most beautiful include those that decorate the Mausoleum of Galla Placidia; the Basilica of St Apollinare in Classe on the southern edgeu o of the city; and the Church of St Vitale, where the mosaic scenes include depictions of the Emperor Justinian and his wife. Other mosaics worth admiring are found in the Orthodox Baptistry, the Basilica of Sant'Apollinare Nuovo, and the Arians' Baptistry.

Adjoining San Vitale is the National Museum, which contains many treasures, including some early examples of Byzantine glass. An admission ticket of €8.50 (£7) covers St Vitale, the Mausoleum and St Apollinare Nuovo; all open 9.30am-7pm daily.

I'd like to see some icons

St Catherine's Monastery, at the foot of Mount Sinai in Egypt, was built by the Emperor Justinian next to a small chapel, founded two centuries earlier beside what was believed to have been the site of the Burning Bush, from which God spoke to Moses and gave him the Ten Commandments. The chapel was decorated with a magnificent collection of icons, which are still in the church, one of the few parts of this still-functioning monastery – the oldest in the world – that are open to visitors (9am-noon Monday to Thursday).

Following the rise of Islam in the seventh century, Egypt ceased to be part of the Byzantine Empire, which saved these priceless works of devotional art from almost-certain destruction. In the eighth and ninth centuries, periods of iconoclasm led to the destruction of many ancient icons within the jurisdiction of the empire. As a result, the rarity of the paintings at St Catherine's, as well as their beauty, makes them all the more awe-inspiring. The monastery is a couple of miles from the village of Al-Milga, where there are hotels and shops.

Trips to St Catherine's are usually included as optional extras by many tour operators, including Kuoni (01306 747002; kuoni.co.uk), offering package trips to Sharm el-Sheikh and other parts of the Sinai.

What happened to the treasures of Byzantium?

Constantinople was sacked by the Crusaders in 1204, and much of its treasure was looted and scattered all over Europe, hence it ending up today in European museum collections. Many exquisite pieces were taken to St Mark's Basilica in Venice (basilicasanmarco.it), itself built in Romanesque-Byzantine style, and kept in its Treasury. A number of objects were removed by Napoleon in the 18th century, but the Treasury still contains a rich collection. Among the exhibits are caskets, incense holders and bowls in silver and crystal adorned with precious stones. The Treasury is inside the Basilica, but opens shorter hours: 9.45am-4pm Monday to Saturday; 2-4pm on Sundays from November until Easter; until 5pm the remainder of the year. Admission €3 (£2.50).

The recently reopened Bode Museum on the Museum Island in Berlin (00 49 30 266 3666; smb.museum/smb), which now incorporates the Museum of Byzantine Art, is another collection to visit. It consists of works from the whole period of the empire gathered from most of the countries that formed part of it. Among the highlights are exquisite carvings and icons from the Byzantine court in Constantinople. The Bode opens 10am-6pm daily, until 10pm on Thursdays; admission €8 (£6.70).

Another important collection can be seen in the Benaki Museum in Athens, an attractive neoclassical building near the city centre, at 1 Koumbari Street (00 30 210 367 1000; benaki.gr), where icons, jewellery, religious artefacts and domestic equipment are all on display, giving a comprehensive picture of life throughout the Byzantine era. Open 9am-5pm Monday, Wednesday, Friday and Saturday; 9am-midnight Thursday, 9am-3pm Sunday; admission is €6 (£5).

More of the Byzantine legacy in Greece?

Thessaloniki, the second city of Greece, was the most important in the Byzantine Empire, and although it has suffered during the course of history from war and fire damage, it is a pleasant, green city on the coast. Since being European Capital of Culture in 1997, it has enjoyed quite a resurgence.

Among airlines operating direct flights to the city are British Airways and easyJet.

Thessaloniki's Byzantine treasures include a number of small churches, such as Panagia Chalkeon, Panagia Acheiropoietos, and Osios David, a building that appears drab from the outside but features a wonderful mosaic of Ezekiel within. The Museum of Byzantine Culture, at 2 Stratou Avenue (00 30 2310 868 570; mbp.gr), is one of the major museums of Greece, and has an extensive collection of artefacts that help to explain the social history of Thessaloniki.

Across Greece's northern border, in the Former Yugoslav Republic of Macedonia, there are a number of Byzantine treasures to be discovered. In Skopje, the capital, the old city – the Stara Charsija – was a thriving commercial centre in Byzantine times. At Ohrid, there are some excellent examples of Byzantine churches, including St Sophia, which has some well-preserved frescoes. A few miles outside the city, close to the Albanian border, you will find St Naum, a monastery complex in a dramatic lakeside location, with, inside, a variety of fine religious art works.

Explore (0845 013 1537; explore.co.uk) runs a 14-night trip to Ancient Macedonia, which will take you to Skopje, Ohrid and Thessaloniki. Prices start at £1,155, including flights, transport, bed and breakfast accommodation and one dinner.

And elsewhere in Byzantium?

Andante Travels (01722 713800; andantetravels.co.uk) offers a choice of holidays in other areas of the former empire. The six-night Bare Bones Byzantium tour, departing on 3 November 2009, focuses on Istanbul, but also includes a trip along the Bosphorus. The trip costs £1,200 per person, which includes flights, bed and breakfast accommodation, and a guest lecturer.

Martin Randall Travel (020-8742 3355; martinrandall.com) operates tours for Friends of the Royal Academy (subscription from £66 per year). During 2009, the company will run a nine-day trip to Byzantine Greece, and a seven-day tour of Istanbul combined with visits to some of the Byzantine churches of Cappadocia. Among other holidays that are available to everyone is a five-day trip in Italy that will include the Ravenna mosaics, Urbino and Rimini.

'Byzantine' Bristol

The city in south-west England was never part of the Byzantine Empire, but for a brief period during the 19th century, a style of neo-Byzantine architecture became popular there. Characterised by decorative arches and coloured bricks, it was used mainly in industrial buildings. Among those that survive is the Colston Hall (0117 922 3686; colstonhall.org), an important concert venue; a former tea warehouse, Bush House, on Narrow Quay, which now houses the Arnolfini contemporary arts centre (0117 9172300; arnolfini.org.uk); and The Granary, pictured, once famous as a nightclub and rock venue, now converted into flats.