The summer school will be held in the Buys Ballot Gebouw (Buys Ballot Building) on the Utrecht Science Park, De Uithof.
You can find the exact locations in the schedule.
(Picture credits: Pieter van Dorp van Vliet)
The Buys Ballot Gebouw is the large building with the large Universiteit Utrecht logo on the roof.Note that you cannot enter the building directly. You may need to enter through the Minnaert building (the low red building in front of the Buys Ballot Building) or the Koningsberger building (the glass building to the right of the Buys Ballot Building).