From sport point of view the Northern part of the lake is a little bit more exciting than the flat Southern part so that's why I write about only this.
Lago di Garda is the largest lake of Italy. It's northern part in Trentino - Südtirol region.
Its length is 51.6km, at the widest part has 17.2km width and the deepest point is 346m. Average depth is 136m. Lake Garda level is 65m above sea level. The surface is 370km2.
As I wrote the northern part of the lake is surrounded by the mountains of Alps and the nearest high peak is Monte Baldo. The southern part is almost on the Po-flat.
Thanks to its position between the German world and the mediterranean world, Lake Garda and its surroundings were inhabited during the centuries and nowadays there are numerous historic resorts that can be visited. Numerous little churches of romanic period are a symbol of a religious and rural life in those ancient times.
The shape is that typical of a morain valley, probably having been formed under the action of a Paleolithic glacier. Although traces of the glacier action are evident today, in more recent years it has been hypothesized that the glacier occupied an already existing depression, created by stream erosion from 5 to 6 million years ago.
The lake has five islands, the largest being Isola del Garda. Nearby is the Isola dei Conigli ("Rabbits' Island") or San Biagio. Both face San Felice del Benaco, on the Brescian side. The three smaller islands are Isola dell'Olivo, Isola di Sogno and Isola di Trimelone.
The main tributary is the Sarca river, while the only emissary is the Mincio River.
Most important towns of the Northern part of Lago di Garda are Torbole, Riva del Garda and Arco. Arco is the paradise of rock climbing.
There are many opportunity to reach this region. There are some airports in the surrounding cities (Verona, Milano), you can go there by car or by or train. I think it is recommended using car or motorbike because the local transportation is a little bit difficult.
You can go from the north from Austria through Brenner-pass (it costs 8€) on A22/E45 motorway (it costs 11€ between Brenner-pass and Rovereto). In Rovereto-South you should turn to the direction of Lago di Garda. This route drives you to Torbole.
If you come from the East you use also the A22/E45 motorway but from the direction of Vicenza and Verona. You should go to the direction of Trento and in Rovereto you can turn to the West to the Lago di Garda. (same route)
You can come from here on A4/E64 motorway from the direction of Brescia and Milano. You should go to Verona turn to the A22/E45 motorway and follow the same route above.
I think there is all time season. You can find fun there every time. Perhaps in summer the place is a little bit overcrowded so it is recommended to use bycicle because there are few parking places close to the lake. It is almost impossible to find a normal place to leave your car in Riva del Garda.
If you want to go climbing to the Sarcatal valley (to the north from Arco) it is easier to go by car.
Red tapeThere are no common rules for climbing. If there is no local prohibition you can climb everywhere.
There are traditional rock climbing routes, aid routes, sport routes, boulder problems, via ferratas and trekking routes in million number. So you can choose the proper gear for the chosen activity. If you forget to bring something there are many good climbing and mountaineering shops in Arco. They have very good prices and big range of equipment and clothes and you can buy there climbing guide books (25-30€).
External linksArco Campeggio (I tried this camping, I suggest to stay there because it's very nice, tidy, full of sporty people so there is no night loudness)
Collection of useful links
Red Point, Arco