My 3 favourite grounds from the many that I've visited on my football visits over the years:
The San Siro, Milan.....
The Santiago Bernabeu, Madrid.....
Arena AufSchalke, Gelsenkirchen.....
And finally, the stadium that had me worried the most when I visited was the Mastella in Valencia. The stand we were allocated when we played Valencia in the CL semi-final actually wobbled when a goal was scored. It also had breathtaking views of the city of Valencia, so something to take your mind off the wobble!! We were stood in the right hand corner of the ground, at the top of the stand, on the picture below.