Codex Alpe Adria 2007 in Udine could be a great starting point to visit other cities and regions nearby. Guided visits and tours are planned during the weekend and on Monday.
Udine (satellite view) is located at the "top right" of Italy, between the Alps and the Adriatic Sea. The city of Udine is the capital of the 600000-inhabitant province of Udine, which stretches from the sea to the mountains. This geographical area is also referred to as "Friuli", whereas the larger region which also includes the provinces of Trieste, Gorizia and Pordenone is officially called "Friuli Venezia Giulia". Udine is the largest province of the region. In spite of the name including the reference to "Venezia" (Venice), Friuli Venezia Giulia is independent from neighboring Venice. Friuli also has a language, which many locals use as a second language (quite a few people think in Friulian and translate into Italian if they have to, slipping back into Friulian after a few sentences).
The countries of Austria in the north and Slovenia and Croatia in the east, and the cities of Trieste in the east and Venice in the south are all within about one hour by car (Italian driving style ;-). The closest beach is about 40 minutes by car (popular resorts include Lignano, Grado and Bibione). The nearby town of Tarvisio (about 50 minutes north of Udine, not to be confused with the city of Treviso, near Venice) is a great starting point for one-day excursions to the mountains.
The ancient towns of Cividale, San Daniele, Aquileia and Palmanova near Udine are less than half an hour from Udine, and you can visit all four in one day, or relax and just visit one or two in an afternoon (Cividale and Palmanova are connected to Udine by train).
If you prefer to spend a full day in one place, returning to Udine for the night, you can consider visiting cities like Milan, Venice or Trieste, or a day at the beach in Lignano, or an excursion to the Alps around Tarvisio.
Udine itself offers a good sampler of Venetian architecture, relatively uncontaminated by major tourist streams, and even by visiting only one or two smaller towns nearby, such as Cividale and San Daniele, you can get a very nice feeling of "real" life and culture.
There are trains between Udine and Venice about every hour, except for a few hours after midnight. You may need to change at Venezia Mestre (there are trains to Venice Santa Lucia every 5-10 minutes). Once you arrive at Venezia Santa Lucia, exit the station, go to the bus (i.e. boat) stop to the right, and take a bus (remember, there are no roads in Venice, so a bus is a boat) to Piazza San Marco, which is the main square. This will give you a nice initial overview of town, and an inexpensive Venice by sea experience. One-way and return tickets are sold at the stops and on the bus (may be slightly more expensive). You can walk back to the train station if you prefer.
There are several early trains to Milan (Milano) which allow you to visit town and be back in Udine before midnight. From the Milano Centrale train station ("Centrale F.S." subway stop) you can take the yellow line ("metropolitana") to Piazza Duomo ("Duomo" stop), where you can visit the cathedral, and you are not far from famous shopping streets (e.g. Via Monte Napoleone). You can take a tram back to the train station for a different experience.
While you can visit either Venice or Milan as a single-day trip from Udine and back, you cannot do the same for Rome (well, you could take a night train both ways, leaving one day to visit the city, sort of). If you have two full days you can do Udine-Venice-Florence-Rome, optionally spending the first day in Venice, the first night in Florence, the second day and night in Rome, and the third night on the train, or the other way around. You could even try to squeeze in a stop in Pisa, which is not far from Florence (Pisa in 60 minutes: take a cab to Piazza dei Miracoli, see the tower, take a few pictures and walk back to the train station). If you visit Venice as a day-trip from Udine this will leave you more time to sleep, and to see Florence and Rome on a separate 2/3-day (or longer) journey. If you carefully plan ahead and are willing to not sleep too much you can do this in a few days as outlined here, with great satisfaction.
Salzburg in Austria is just two and a half hours North of Udine (by car, it takes longer by train), and is not far from Munich (München), in Germany. Or you could take a train to Vienna (Wien), Austria...