Apparently that's the common English pronunciation of the town. I learned it pronounced as "SEE all" years ago , but recently I've been told that's wrong too.
I really wish Duolingo had a better text to speech program. It's Korean pronunciation is noticeably bad even to people who don't natively speak Korean.
Actually it's not that bad. But there are plenty of resources online that discuss Korean phonology, if you'd like to figure out how everything is actually pronounced. 서울 is pronounced /sʌ.ul/, approximately "suh-ool".
If you listen closely, or listen to a Korean person say it, they pronounce it as two syllables. So it is very similar to the English word soul but not quite as soul is a one syllable word :P
Does anyone else hear dondon when the person says london while reading the Korean spelling of it.
I don't think they should pronounce the words. It makes it too easy. I'd rather try and read the Korean words without it telling me what they are.