Most of the villages around Valencia have outdoor swimming pools which open during the summer months (July and August). These are incredibly cheap (less than a couple of euros to get in) and you can spend the whole day there.
The easiest ones to get to are those served by Valencia’s metro. Try Rocafort (right next to the station), Moncada (a bit of trek from the station, but in a nice location on top of a hill) or Betera (quite far from central Valencia, but the swimming pool is one of the best).
Moncada - POLIDEPORTIVO MUNICIPAL BADIA – PEDRERETA,
C/ Lepanto final.
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