Lake Zurich is big: 25 mi (40 km) long and 1.9 mi (3 km) wide. At its deepest it reaches 469 ft (143 m). The water is very clean, coming off those Swiss mountains, and is used for supplying water to the cities around it. The largest of these is Zurich at around 360,000 residents.
The lake is used for boating and swimming, reaching up to 20 degrees Celcius (68 F) in summer. Along its edges are dotted swimming pools - these are floating pontoon decks with change rooms, sunbathing areas and usually saunas, massage and a cafe. They are open May-October. Parks line the lakeside and fill with people picnicking, roller-blading and sunbathing in summer. Even the police patrol on rollerblades!
Zurich wraps itself around the lake so it's not hard to find. There are lovely paths and parks beside the lake so buy an ice-cream and take a stroll.