When you enter Utrecht, you cannot miss the Dom Tower. Once upon a time this tower was connected to the Dom church, but a bomb during the World War destroyed part of the church. The church was rebuilt but much smaller and a street was built between the church and the tower.
Nowadays you can climb the tower with a guide (tickets for sale at the small building connected to the tower). Be prepared though: there are many many many steps to be conquered before you reach the top and enjoy the spectaculair view of Utrecht.