I just played one game trying cultural victory. I played in huge map but normal speed. And according to civilopedia, I should have three cities achieve legendary. And the point should 50000 for normal speed. Please see the screenshots and my saved game. I achieve 50000 for 3 cities, but nothing happened. 
When I check the culture bar in the city, it seems suggest 100000 is required for next level (legendary). 
Is that because I play in huge map? That is so confusing and I feel 100000 is too hard... I still need more than 100 turns to achieve.
When I check the culture bar in the city, it seems suggest 100000 is required for next level (legendary). Is that because I play in huge map? That is so confusing and I feel 100000 is too hard... I still need more than 100 turns to achieve.
So 100000 for Legendary...
