To walk up to the Castello , go through the Arco Bollani , designed by Palladio, and onward up the graceful Venetian Gothic gallery, the Loggia del Lippomano on the right. The sixteenth-century castello , built and decorated by local artists, houses an excellent Galleria d'Arte Antica (Tues-Sat 9.30am-12.30pm & 3-6pm, Sun 9.30am-12.30pm; L4000/2.07, free Sun), containing works by Carpaccio, Bronzino and Tiepolo, as well as an indifferent Carvaggio and an interesting historical painting by Palma Il Giovanni showing St Mark putting the city under the patronage of St Hermagora, first bishop of Aquileia; Piazza LibertA  is clearly visible on the right. There are fine views across the city from the grassy terrace outside the castle, a good spot for a picnic.

North from the Piazza LibertA  is Via Mercatovecchio , once the mercantile heart of the city and now the busiest shopping street. The little chapel of Santa Maria , incorporated into the Palazzo del Monte di PietA  in Via Mercatovecchio, is a beauty: viewed through the glass booth from the street, the interior, with its cloudy Baroque frescoes by Giulio Quaglio (1694), has a pristine, subaqueous appearance.

Due west lies the Piazza Matteotti , with galleries on three sides and the fine Baroque facade of San Giacomo on the fourth. The square's importance as the centre of public life in Udine is proved by the outside altar on the first-floor balcony of San Giacomo ; mass was celebrated here on Saturdays so that selling and buying could go on uninterrupted in the market below. As well as being the town's main market, this was the setting for tournaments, plays and carnivals. The fountain in the middle of the square was designed in 1543 by Giovanni da Udine, a pupil of Raphael, who also had a hand in building the castle.

Off the south side of Piazza LibertA  is the Duomo (7am-noon & 4-8pm), a Romanesque construction that was given a Baroque refit in the eighteenth century. Altarpieces and frescoes by Giambattista Tiepolo are the main attraction - they decorate the first two chapels on the right and the chapel of the Sacrament, a little way beyond. A series of frescoes painted by Tiepolo in collaboration with his son, Giandomenico, can be seen in the tiny Oratorio della PuritA  opposite - ask the sacristan in the duomo to show you.

But Udine's outstanding works of art are the Giambattista Tiepolo frescoes in the nearby Gallerie del Tiepolo in the beautifully furnished Palazzo Arcivescovile . Painted in the late 1720s, these luminous and consummately theatrical scenes add up to a sort of Rococo epic of the Old Testament. Fall of the Rebel Angels is the first work you see as you climb the staircase, while the finest room, the Gallery, is at the top, immediately on your right. Every surface is painted with either trompe l'oeil architectural details or scenes from the story of Abraham, Isaac and Jacob. To the left is a sequence of rooms decorated in rich colours: watch for Tiepolo's Judgement of Solomon in the Red Room, and Bambini's wonderful Triumph of Wisdom in the serene Delfino library. Also inside the Palazzo Arcivescovile and arranged around the Tiepolo galleries is the Museo Diocesano , with an assortment of sculpture and funerary monuments, as well as an exhibition of naive art - popular sculptures from Friuli's churches spanning the Gothic, Renaissance and Baroque periods.

On the edge of the old town in Piazza Diacono, the Galleria d'Arte Moderna (Tues-Sat 9.30am-12.30pm & 3-6pm, Sun 9.30am-12.30pm; L4000/2.07, free Sun) gives a reasonable overview of Italian art in the twentieth century, plus a glimpse of a few foreign greats.