If you are accosted by a boatload of horned-helmeted Vikings when strolling Dublin\'s streets, do not be alarmed. Outfitted in plastic helmets and roaring fiercely, Viking Splash Tour participants are encouraged to embrace the Irish capital\'s Viking heritage as the amphibious contraption travels the city\'s roads and waterways.Much of Dublin\'s early history is as murky as the peaty basin where the River Liffey joined the now-underground River Poddle, near the site of what is today the Dublin Castle gardens. The tidal basin formed by the two converging rivers was named \"dubh linn\" (meaning \"black pool\") by Celts, who had inhabited the area upstream as early as 500 BC. The Celts were settled at a ford over the river, near the present-day Father Mathew Bridge on Church Street, hence Dublin\'s Irish name, Baile Átha Cliath, meaning Town of the Hurdle Ford. Marauding Viking Norsemen from Scandinavia encountered the basin on their seasonal plundering voyages around the early 9th Century. Its location gave them refuge from the northern sea storms and access to the ship building materials found in Ireland\'s dense forest. Clashes notwithstanding, the enterprising Vikings stayed on, integrating with the Irish Celts and establishing a “longphort” (raiding base) around 841. Dubh linn evolved into the settlement of Dyflin, which swelled to become a major trading empire with countries as far afield as continental Europe, the Middle East and North Africa. Precious metals, fabrics, weaponry and horses were all traded here, as well as humans -- Dyflin had the biggest slave market in Europe following the fall of the Roman Empire. Although Dublin’s history is still shrouded in uncertainty, it is becoming clearer as Viking remains continue to be discovered in the city. In 1961, when construction began on the Dublin City Council headquarters at Wood Quay -- the area between the Liffey and Christ Church Cathedral  in  south Dublin -- an extensive Viking settlement was uncovered. The cathedral itself was built on the site of a Viking church. A bridge leads from Christ Church Cathedral to the attached old Synod Hall, which now houses the excellent Viking exhibition Dublinia. Displays include artefacts unearthed at Wood Quay, a reconstruction of a Viking house and instruction in decoding the Viking runic alphabet. If you are moved to don a horned helmet yourself, dressing up in marauding Viking style (or chained slave style) is part of the Dublinia experience too -- perfect for kids. On the cathedral\'s eastern side, the Viking-established Fishamble Street is Dublin\'s oldest street at the western end of Temple Bar. Artefacts from the Wood Quay excavations are also displayed at the archaeology and history branch of the National Museum of Ireland. Swords, bows and jewellery made from amber, bronze, silver and gold are among the rich finds, along with board games, toys and run-of-the-mill items like needles, spindles and even a whalebone “ironing board” once used to smooth cloth. In the past decade, several Viking graves from pagan warrior burials have been unearthed south of Dublin Castle on Ship Street Little, South Great Georges Street and Golden Lane. To tread the streets of Viking Dublin with entertaining commentary along the way, Hidden Dublin Walks runs walking tours of the city, relaying its often-brutal beginnings. And if you are in Dublin in mid-August, you can celebrate the city\'s feisty Viking history at the Dublin Viking Festival, where a Viking craft village is the central attraction. There are also readings, re-enactments and combat displays -- and costumes including horned helmets, of course.