"Transport from airport to Leuven centre - "
Hi Aline!
The festival must be in the beginning of August, you will have to check the website of Marktrock on time
The closest airport from Leuven is Brussels Airport in Zaventem. The transport between the airport and Leuven is very good.
There are direct trains that goes to Leuven city.
I stronly advise you to go druing that festival, you will have nice evenings on the cozy market place with a fresh cold Belgian beer in your hand!