as an addition to the city improvements already available a tourist option would also be a nice addition as it would allow nations to build up a large tourist network i do have ideas for some projects or improvements for this topic
improvements
Airport (regular) - $250,000 and 500-1000 steel, allows for 250 passengers to pass through every turn depending on city attractiveness e.g low crime, low disease and low pollution max 3
hotel - $125,000, allows for accommodation for a maximum of 500 guests max 5
cruise ship terminals - $300,000, allows to bring in 1,000 temporary guests that leave after a few turns, duration of stay depends on pretty much the same as the Airport standards
this would increase the commerce, GDP and a new tourist rating for the city and nation a leader board could also be introduced for the nations with the highest tourist rating whoever has the highest receives 20% more tourists there will be certain aspects that reduce tourist rating however including if your nation is at war or if you are inactive there could also be a part where if your popularity drops below 20% at random some kidnappers could capture tourists or bomb airports this would make players keep their approval up and remain active as if they dont respond within 2 turns their tourists rating drops by 5%
projects
Airport (international) - $20,000,000 and 5000 steel, increases the amount of tourists arriving by plane by 50% in all cities where there is an airport
National Landmark - $15,000,000 - increases income from tourists from $100 per day to $500 per day
National Tourist Board - $10,000,000 increases the amount of tourists overall
if you have any ideas please mention them below