I like Titian. I like the way he gets his fingers into the paint and muddles the colours about. And where else could a painter with such a sensuous relationship to colour come from, other than Renaissance Venice? It's no surprise that his career began there, yet the first surprising factoid of the National Gallery's new show, Titian's First Masterpiece: The Flight into Egypt, is that he wasn't a native of Venice at all. He was born in a tiny town in the Italian alps. Look into the top corners of any of the paintings in this show, where the decay of fugitive green pigment gives those far-off, blue remembered hills on the horizon their startling and unlikely blueness – that’s the landscape Titian grew up in. Not Venice, with its sun-bleached marble and green canals.

But then so many of the artists working in the city when Titian began his apprenticeship were not native-born either. Giorgione, another outstanding talent, was plucked from the provinces about a decade earlier to train in the workshops of Bellini. Four of his works (there are fewer than a dozen in existence) join the Titians here, and are a particular joy. Then there were the northern artists lured to the city – Dürer, most importantly. But as this show demonstrates most ably, paintings, sketches and ideas were travelling back and forth across the Alps in a constant cross-fertilisation. Think of Venice as an artist’s palette, and imagine these different influences pouring into it. It must have been an astounding place to find yourself as a pipsqueak of an artist with a paintbrush in your hand.

The artists’ patrons were Venetian, however, and the most significant was Andrea Loredan who commissioned The Flight for his palace. Venice has no such natural landscape, of course: unlike any other Italian city you didn't look over your balcony to vineyards and hills beyond, you looked out at palazzi and the Venetian lagoon. Perhaps that’s why landscape art was fired into such early life here, in the same way as we hang photographs of tropical beaches in windowless offices. The gallery’s accompanying publication – very reasonably priced at £9.99 – explores the origin of ‘the landscape,’ and will no doubt be on many a bookshelf for years after the star of the show has returned to the Hermitage.

So is the painting itself a masterpiece? It’s certainly a step-up in terms of scale from the other landscapes exhibited, at more than 3 metres wide. Titian would still have been in his teens when the painting was unveiled in about 1507, and for such a young man, even the attempt to organise such a big canvas is breathtaking. You do get the feeling that Loredan would have displayed his new possession very proudly. It is, for example, vastly more accomplished than Homage to a Poet of 1500 (attributed to Giorgione or his circle), where a perfect Italian Renaissance landscape is populated by beasts and figures straight out of a late medieval pattern-book. But is it better than Titian’s own portraits? Four of these greet you as you enter the show, and the expressions on their faces suggest they wouldn’t have thought so – such an outré subject as landscape would never be taken seriously, they seem to say.

Because the subject-matter is unusual: Titian’s landscape is a very busy place. As well as the Holy Family in the foreground, it contains a soldier (clearly lifted from Giorgione), a bull, sheep, stag, eagle, fox and symbolic burst of scarlet roses. It has the atmosphere of a Flight into Egypt crossed with the Garden of Eden. The landscape is wide and open, and takes you right back in the far distance to the mountains. You can see the river moving through the beautifully untidy and completely convincing stand of trees. The different ingredients are perhaps not perfectly integrated into the whole, but this is real countryside – winds blow, leaves move, draperies billow and shine, the stag scents the air, racing clouds obscure the sun. The figures leave only the tiniest of shadows behind them. And then there is a mysterious fourth figure leading the donkey. He has the most angelic face, but no wings attached to his shoulders. He holds a bundle of possessions gathered under his cloak and is glancing back to check that Mary and her son are still safely seated on the donkey and that a very weary-looking Joseph is still following along behind. Who is he? It is almost as if Christ has been given a helpful older brother.

The Flight into Egypt has been in Russia since 1768, and in conservation for more than a decade. Here it is shown restored not only in terms of its appearance – the donkey being the only area where substance has been lost – but in terms of its historical context too. As the National Gallery claims, quite rightly, it is probably the only gallery that would be able to serve this work so well, gathering around it paintings, etchings and drawings that demonstrate not only who Titian was emulating, but who he was pitting himself against. It’s an argument in itself for value of the National Gallery’s holdings. It’s a treat. It’s engaging and accessible, and it displays a work that after its present outing will not travel again in our lifetimes. It’s also free. One and a half rooms, 28 works, four Giorgiones, two Bellinis, five Dürers and eleven Titians, plus a stroll across an Italian meadow. What, as Andrea Loredan might have said, is not to like?

Titian's First Masterpiece: The Flight into Egypt, at National GalleryErato reviews Titian's First Masterpiece: The Flight into Egypt at the National Gallery4