The Spread Culture espionage mission is available in any foreign city where we have some culture on the city tile.
It adds city culture worth 5% of the total from all players in that city (so that the total goes up exponentially), at a base cost of 3EP per culture point added (as well as a little bit of tile culture). Of course, that will be drastically reduced by the various discounts we can get - trade routes, holy city, stationary spy, etc.
This is only really effective in cities where there's already significant native culture - if there's 500 native culture it'll take 95 spy missions, compared with 36 if there's 10000 native culture.
Of course, we then have to capture the city afterwards for it to count as Legendary.
edit: The only reason to consider this is because in a large empire we can generate espionage faster than we can generate raw culture in one city and great artists.
It adds city culture worth 5% of the total from all players in that city (so that the total goes up exponentially), at a base cost of 3EP per culture point added (as well as a little bit of tile culture). Of course, that will be drastically reduced by the various discounts we can get - trade routes, holy city, stationary spy, etc.
This is only really effective in cities where there's already significant native culture - if there's 500 native culture it'll take 95 spy missions, compared with 36 if there's 10000 native culture.
Of course, we then have to capture the city afterwards for it to count as Legendary.
edit: The only reason to consider this is because in a large empire we can generate espionage faster than we can generate raw culture in one city and great artists.