Cayenne

I play Simcity4Deluxe for like 2 weeks now. I had city of 100.000 residents (30000com jobs and 8000industry jobs) but the biggest commercial building only had 1000 wrokers and looked like Rock Bottom Terrace :-\ (CO$$$ demand was quite high) My question is what city/region population size you need for skyscrapers to develop? Btw i'm working an a city now it has only 46000 residents yet (70000 in region) but no nice downtown so i'll post later