After a cold climb inside the Reichstag Dome, we looked forward to the warmth of Einstein Cafe on Unter de Linden. Lunch was terrific, with one of us having succulent house-made frankfurters with a crispy exterior and perfectly balanced seasoning, over a rich goulash sauce. Surprisingly, a wonderful avocado toast with grilled tomato was also offered, and served over a whole-grain, hearty sourdough bread. Service was cheerful and professional, seating very comfortable, and the Cafe provided a fortifying and warming break on a busy but bitter-cold day.