Great place for Bulgogi and the original place of a small street food success story in Berlin. 

Wim Wenders shot Wings of Desire here. It's a quiet place to work and definitely a gorgeous place to visit. Combine it with a visit to the Philharmonic, just across the street. Affiliation is 30 euros per year and you have lots of desks all over the library to choose from.

Cosmoveda is a hidden xberg gem. It's an Ayurvedic supermaket that happens to come with a kitchen with it. There you can find a delicious Ayurvedic lunch menu (with soup, main and a little dessert) in 3 different sizes, prices starting at just 5,90. Not to mention you can shop the ingredients that you just ate in case you want to try to cook Ayurvedic yourself.  

Spindler is my favorite brunch stop when I'm in the mood for fresh eggs and classy but-yet-simple athmosphere. 

Just until recently this place used to be one big old Aphoteke (Pharmacy). They have kept the Apotheke's  dark wood Art Deco charm to use in benefit of great coffee and fantastic brunch (try the french toast and you'll see I'm not lying).