One of the best days in Hungary was spent in Siófok on Lake Balaton. Just an hour and a few dollars for the train ticket, just outside Budapest you can experience how the average Hungarian experiences summer holiday. Lake Balaton is very shallow, so you are able to walk very far out into the water, motor boats also seem prohibited in much of the lake so it is peaceful.
While there is a free public beach, take my advice and go to the one of the pay beaches. The best 3 dollars I have ever spent. You get a nice grassy water side lawn, little cafes and clean bathrooms (watch out for the ladies who are unofficially manning the bathrooms—they are not staff of the beach, no need to tip them).
This was a great way to get away from the city, and I think we were some of the only tourists there. So much so at the gyro stand I stopped at, the guy behind the counter insisted he bring me my gyro while everyone else was just doing walk up service. They sure know some hospitality.