Finding your way in Seoul, South Korea

I suppose, that reaching some places in Seoul without GPS is almost impossible.
First, I realized that all maps in subway ignore completely world directions - matching them with guidebook maps is quite a challenge. And source of serious confusion.
Second, some streets seem not to have names. But they are there. :)
Third, buildings are numbered according to building permit approvals, which means the younger the building, the higher the number. This also means that you will see building 21 close to 150, which doesn’t make sense to most of foreigners. And creates even more confusion.