Zemplínska Šírava is very nearly Slovakia's largest body of water (the Orava reservoir in the northwest is slightly bigger) and like most of the country's large lakes it is man-made. It was created in the 1960s and quickly became a major holiday destination.
It remains popular today, though many Slovaks now prefer to make the journey to the Adriatic or to Greece for a beach holiday. Zemplínska Šírava's origins mean that its 'beaches' are in some places just grassy fields which slide into the water. That said, the northern shore is pleasantly laid out and if you squint (quite hard) you could almost be in the Mediterranean.
Some of the public buildings have seen better days, but there are a number of good-quality pensions in the resort villages lining the north side of the lake (the south shore is less developed). One of them, the EuroPenzión Salaš, has a band of very good musicians to entertain diners with gypsy-style music in the restaurant.
One advantage of the lake being a shallow reservoir is that the water heats up in the summer (the summers in this region being fairly reliable) and is pleasantly warm to swim in. If you don't fancy a dip, there are boats for hire and, in July, an outdoor folk festival which attracts musicians and dancers from around Slovakia and the neighbouring countries.