Zagreb's reputation as a fun-loving city doesn't go into cold storage for the winter. Outdoor festivities continue into January with markets and concerts, as the locals trade their summer beers for mulled wine. The neighbouring mountain, Medvednica, also comes into its own, with its small ski centre (4km of varied slopes: pp-medvednica.hr), just a half-hour's journey by tram and cable car from the centre.
Zagreb's upper town, Gornji Grad, rises proudly above the plain where the rest of the city is arranged in a grid of uniform avenues. By contrast, Gornji Grad's cobbled, medieval streets span two hills (Kaptol and Gradec) and are filled with striking buildings and a healthy number of museums. This is by no means a fossilised tourist trap, though; a walk through Gornji Grad is as much a window on Zagreb's daily life in as it is on the city's turbulent past.
Start in Zagreb's central square, whose lengthy name, Trg Bana Josipa Jelacica, is mercifully shortened by everyone to "Trg", (The Square). Take Bakaceva Street, which slopes up beside the tourist office, towards Kaptol's focal point, the cathedral (free; 10am-5pm daily, from 1pm on Sundays; 00 385 1 481 4727). Startlingly white, it sports 108m-high twin spires – one of which is being restored and looks like a bandaged arm – that dominate the city skyline.
Head west from the cathedral square and down the steps to Dolac, the city's most atmospheric market. Between 6am and 2pm every day, it's filled with the bright colours and the scents of fresh fruit and vegetables; it's particularly lively on a Saturday, when many Zagrebians come to buy from the same stalls where their mothers used to shop.
Another flight of steps leads downwards from the south west side of the market to Zagreb's best-known party street, Tkalciceva. Once the course of a river separating the two hills of the Old Town, it's now a flow of pastel-coloured two-storey houses with balconies, every one of which is a bar, restaurant or café. Try the local Medvedgrad beers in Pivnica Mali Medo at number 36 (10am-midnight, noon to midnight on Sundays; 00 385 1 492 9613; pivnica-medvedgrad.hr). A half-litre glass costs 14 kuna (£1.65).
Retrace your steps back down Tkalciceva and turn right down a street with the poignant name of Krvavi Most, "Bloody Bridge". It recalls the disputes that used to take place in medieval times between the residents of Kaptol (the church-dominated community) and those of Gradec, the secular district on the neighbouring hill. You reach the latter after a right turn into Radiceva, followed by, after 400m, a sharp left turn through Kamenita Vrata, the 18th- century Stone Gate. As your eyes become accustomed to its dark interior you will see candles flickering and people at prayer. Legend has it that when fire destroyed the original wooden gate, a painting of the Virgin Mary was miraculously spared. Since then, the gate has been a shrine where residents of Zagreb pray for good luck in all matters of life and death.
Follow Kamenita Street from the gate until you reach St Mark's Square, Markov Trg, the centre of Gradec and the heart of Croatia. On your left is a long Baroque building with a butterscotch-coloured façade, now the seat of Croatian government. Opposite is the slightly grander stone Parliament building, while in between them is the church of St Mark (Sunday 7.30am-6pm; 9am-noon on other days; free ; 00 385 1 485 1611). On Saturday and Sunday mornings the square is the setting for the ceremonial changing of the guard, ancient in appearance but recently introduced. The start of the event is signalled by the thunderous boom of a cannon, which is fired at midday on the dot, scattering pigeons, causing locals to check their watches and sending first-time tourists diving for cover.
Cirilometodska Street leads south from the square towards, at number 2, the latest and most intriguing of Gornji Grad's museums: the Museum of Broken Relationships. Exhibits that encapsulate or recall the end of a relationship are accompanied by a short text telling the story of the break-up. There's an unworn wedding dress, a teddy bear and an axe, which was applied to the furniture of a cheating lover (daily 9am-10.30pm; 25 kuna/£2.80; 00 385 1 485 1021; brokenships.com).
Carry straight on from the museum down Dverce Street to the Strossmayerovo Boulevard, which winds along the southern edge of Gradec and is the summer venue for evening concerts. In winter, it dazzles with views across the lower town. You can get back down to the main square by the funicular railway (5 kuna/65p) or via several flights of steps.
Better still, interrupt your descent with lunch (or dinner) at the beautifully-situated restaurant Pod Grickim Topom (00 35 1 483 3607; restoran-pod-grickim-topom.hr; closed Sundays) at Zakmardijeve Stube 5, with views of the town below. The menu uses seasonal ingredients from Dolac market and includes dishes such as beef tagliata with grilled vegetables and home-made goat's cheese ravioli with sage butter; mains cost about 100 kuna (£11).
Continue down the steps to reach the main square again.
Advent is celebrated enthusiastically across the city (adventzagreb.com). The central square of Josip Jelacic hosts an ice rink and music concerts every evening between 5pm and 9pm, weekends 10am to 2pm. In the surrounding streets, there's a traditional Advent Fair, with stalls selling gingerbread cookies, trinkets, Christmas decorations and souvenirs.
New on the accommodation block, and an economical alternative to the traditional hotel, is the small, stylish B&B Studio Kairos (00 385 1 46 40 680; studio-kairos.com). It's a 10-minute walk from the main square at Vlaska 92, with doubles starting at €48 (£39), including breakfast.
Mick Webb travelled as a guest of Croatia Airlines and the Zagreb Tourist Board.
The new daily service between Heathrow and Zagreb with BA (0844 493 0787; britishairways.com) joins Croatia Airlines' six flights a week (020-8745 4683; croatiaairlines.com), while easyJet (0834 104 5000; easyJet.com) flies from Gatwick.
Best Western Premier Astoria, Petrinjska 71 (00 385 1 480 8900; hotelastoria.hr). Doubles start at €101 (£81) including breakfast.
Croatia Tourist Board: 020‑8563 7979; croatia.hr