Conveniently located in the bottom of the Hauptbahnhof, Siglo is a great Asian market that has more…read moreor less everything you'll need on a quick shopping run. Open on Sundays (YAYYYY- this is why I shop around the Hbf), you can find anything from udon noodles to massaman curry mix to mace to unoki mushrooms. Korean, Thai, Japanese, Chinese, Indonesian...it's all covered. Food from the subcontinent is not, for the most part. The staff is very friendly and super helpful, but beware, you must pay with cash (unless it is over 10 Euros I believe, but don't mark my word on that). They also sell accessories, kitchenware, and anything else you may need to eat a complete Asian meal.
The reason I don't shop here more often is because there are better and bigger Asian stores. And those better Asian stores are cheaper. Quite a bit cheaper, in fact. I also prefer a variety of goods and since it is missing Indian products, I find it easier to head up Kaiserstraße to my beloved Spicelands and the Asian markets on the that street. But if you're hanging around underground and don't feel like walking through the 'interesting' streets around the Hbf, this place is for you!