Steven Van de Velde, 21, pleaded guilty at Aylesbury Crown Court to three counts of rape against a child.
The court heard how he travelled from Amsterdam in August 2014 and raped the girl near Furzton Lake, and at an address in Milton Keynes.
Van de Velde, who will be sentenced in March, returned to the Netherlands, but was extradited and arrested in January.
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The court heard how Van de Velde, of Cornelis De Wittlaan, Den Haag, was aware of the girl's age, having had conversations on various social networking sites.
A survey for CBBC Newsround suggests more than three-quarters of children aged 10 to 12 in the UK have social media accounts, even though they are below the age limit of 13.
A Dutch international volleyball player travelled to Milton Keynes and raped a 12-year-old girl he met on Facebook.