What better way to explore chic city culture and the history of Eastern Europe than onboard a recent addition to P&O's fleet, the Artemis. Peter Mason braves the seas.

We'd been looking forward to our luxury cruise with the anticipation of a three-year-old on Christmas Eve.

To cruise virgins like ourselves, the name Artemis suggested something like the old Royal Yacht Britannia, all polished brass and oak-panelled cabins. P&O's brochure talks lyrically of the thrill of dressing for formal dinner, which sounds so much nicer than superliners pumping out grub around the clock. Once on board, we soon discovered that Artemis is, in fact, the 20-year-old Princess Royal, revamped and rebranded for the UK market.

The company says its intimate, friendly atmosphere and "child-free environment" appeals to both past passengers and experienced cruisers. At 46,000 tonnes, she's dwarfed by the superliners - a key part of her appeal. Much care and attention to detail was lavished on spacious and wellthought-out public rooms, before Artemis re-launched onto the market in summer 2005.

Cabins still show traces of their 20-year legacy in the hands of another owner. But they are comfortable and cosy, more than adequate for the ship's 1,000-odd passengers. There's also an excellent choice of activities on offer and the food was some of the best I've tasted anywhere.

As for the lack of children - well, it might not suit everybody but it suited us this time. Every time we landed, local parties were celebrating Midsummer. From Latvia to Estonia to Finland to Sweden, celebrations erupt around June 21. Locals, intent on living it up, sometimes had more holiday spirit than us.

In Riga, Latvia's capital, we were greeted by girls in national dress, their hair garlanded with oak leaves and flowers, and the partying carried on from there.

In Tallinn, capital of neighbouring Estonia, it was more of the same 24 hours later. Midsummer day was over, but who were we to complain?

The Finns take midsummer even more to heart. In winter, the sun barely rises above the horizon for months on end - so the country throws off its winter mantle at first sign of a sunny day and celebrates like there's no tomorrow.

In Oslo, Midsummer Sunday meant almost the entire population had abandoned the city for weekend cottages and summer retreats. On our city tour, the Holmenkollen Hills gave us splendid city views and Oslofjord. Hans Christian Andersen is a national treasure to the Danes, so at Aarhus, our next stop, we were greeted on the quayside by actor Torben Iversen and his troupe enacting scenes from the author's best-known works. En route to Riga, we had our first glimpse of the legendary midnight sun. Though the sun dips low on the horizon, and the sky goes pink, for the most part the light remains. Sitting on our balcony reading a book at midnight, was eerily unforgettable.

Latvia, a tiny country of just two million, survived centuries of foreign occupation - Sweden, Germany and Tsarist Russia have been among the country's other rulers - but its dignified people take pride in showing off their forested countryside and capital city.

But the highlight of this voyage, at the eastern tip of the Baltic, is surely St Petersburg, old capital of Tsarist Russia. The 'Venice of the north' is truly splendid: canals, Renaissance architecture, gilded palaces and magnificent onion-domed churches, all topped off by the jewel in the crown, the Hermitage Museum, with three million works of art.

In Stockholm we tackled both the Vasa museum (for Sweden's answer to the Mary Rose) and the Stadshuset, or City Hall (which emulates the Doges Palace in Venice, and is home to the annual Nobel Prizegiving banquet).

Nine cities and seven countries in 13 days is a test of any ship, its crew - and passengers. So we probably needed the day at sea en route to Copenhagen - our penultimate port before heading home.

HOW TO GET THERE

Peter Mason sailed with P&O Cruises.

In 2007, 14-night Baltic voyages, departing from and returning to Southampton, start at £1,319 per person sharing twin cabin.

P&O Cruises

Reservations: 0845 678 0014/www.pocruises.co.uk

ENJOY THE SIGHTS - ON DRY LAND AND OFF SHORE

Copenhagen: Hans Christian Andersen.

St Petersburg: Hermitage Museum.

Stockholm: Nobel peace prizegiving.

Cosy: The Penthouse on the Artemis.

Live it up: The Atrium on the Artemis.