city summer style

Early summer in Europe....what to pack? 
Sure, there will be my ballerina's for city explorations, nude pumps to combine with cocktails, jeans and the "oh-so-reliable" trench.......(looking for more space in my luggage), but what else?
A better idea would be to pack the bare essentials and shop for everything else (not sure my credit card would appreciate this one). Looking forward to Hamburg next week.  

"There's a time each year
That we always hold dear,
Good old summer time;
With the birds and the trees'es
And sweet scented breezes,
Good old summer time,
When you day's work is over
Then you are in clover,
And life is one beautiful rhyme,
No trouble annoying,
Each one is enjoying,
The good old summer time."

-  Lyrics by Ron Shields, 
In the Good Old Summertime-