On the lake surrounding the city of Mantua, we find our hotel barge, La Bella Vita, peacefully moored. A glass of prosecco – the first of many – accompanies introductions to the crew and fellow passengers before we set off for our first shore visit. A few minutes' walk along grassy banks takes us beneath the imposing walls of St George's Fortress and into the cobbled main square of the city.
A stark, 13th-century brick façade with swallow-tail battlements heralds our arrival at the city's Ducal Palace. This is the expansive home of the Gonzagas, who ruled this city with an iron fist – a prison cage still hangs from a nearby tower – as well as remarkable cultural patronage. Moveable works have mostly been dispersed; many were sold by impecunious late Gonzagas, including to our own King Charles I. But much remains: large-scale frescos, classical statuary, tapestries, carvings and hanging gardens. There's also the glorious Camera degli Sposi (Bridal Chamber) by Andrea Mantegna which has reopened following restoration work.
Just across the medieval centre of town, the church of San Andrea is a Renaissance masterpiece, and the burial place of painter Andrea Mantegna. It is newly restored and looking splendid after eight years and €9m of work. We revel in the new clarity of the frescos before meandering back through evocative streets of pastel-shaded townhouses, 500-year-old palazzi and narrow canals, to our floating home.
The engine gently humming, La Bella Vita pulls away from the shore and purrs under a low bridge ("heads down on deck!") on to the River Mincio. Trees replace fortress walls; herons, egrets and cormorants are our only company. It is immensely peaceful. We moor near Governolo, where the Mincio meets the Po. Bikes are prepared by the crew and three of us set off for an evening ride.
I am glad to work up an appetite; our chef, Andrea, crafts wonders in the galley and there are local specialities at every meal. We enjoyed pumpkin ravioli and crumble cake from Mantua; seafood risotto (rice is grown in this watery region); aged asiago cheese with delicious pear marmalade, Grana Padano (Padana is the valley of the Po); and much more, served with local wines and liqueurs. Over long, leisurely meals the 15 passengers quickly merge into a rather unlikely houseboat party.
I awake to find we are on the move. Pulling up the blind in my cabin I see a fish leap from the water. We pull into a large lock beside which goats are grazing while a handsome cockerel struts among them. If water levels are too high or too low La Bella Vita travels on the ancient canal parallel with the river but we are entering the Po itself – the longest river in Italy, Fluviorum Rex (King River) as local boy Virgil called it. It is the source of this region's wealth: the Po created the nation's most fertile plain and a complex trading network of watery highways. Now, though, the traffic is largely on land; the river is quiet as I gaze from the sundeck.
Over the flood-defence embankments peep bell towers and churches. Altars here do not point east; churches face the river – God-like giver, and taker, of life. The Po's high-water marks are recorded on a slab of white marble in the centre of Ferrara. This "Padimetro" goes back as far as 1705 and the peak is the devastating flood of 1951.
Today, Ferrara lies a few kilometres from the water but at the time of its Este family rulers the city-state sat right on the Po and the court retained a full-time river official. The medieval fortress-palace that was childhood home of Isabella d'Este – and once marital residence of Lucretia Borgia – dominates the centre of town.
A tour of Ferrara's Unesco World Heritage sites takes in other Este palaces, Italy's best-preserved Renaissance city walls, the medieval old town and the towering duomo. I am reluctant to leave, but we have much to do. We have wine to taste at a classic Italian villa, and a visit to 17th-century Villa Ca'Zen, where Byron's illicit assignations with a lady of the house resulted in his Stanzas to the Po ("What if thy deep and ample stream should be; A mirror to my heart"). The Po travels many routes to the sea. We take the Po Levante to charming little Chioggia – a mini, more intimate, Venice.
Our destination is now in sight. The campanile of St Mark's and the long wall of the Doge's Palace rise up ahead. This is the perfect way to arrive in the city-state that is the region's superpower.
We moor along the waterfront. We visit the Doge's Palace and St Mark's Basilica before dinner and drinks on deck, marvelling at the view. In the morning we are obliged to take our leave of the aptly named Bella Vita, but life still feels pretty good as I wend my way into the heart of Venice.
European Waterways (01753 598555; gobarging.com) has a six-night Bella Vita cruise between Venice and Mantua, including all food, wine, open bar, excursions and local transfers. Cruises run from late March to late October and the price is £2,290pp in "value season" (selected dates in March, April, July, August and October), and £2,590 at other times. Excludes flights.