Etherpoly.io

Etherpoly cities generate passive OLY income, that can be boosted by upgrading to houses, offices, hotels or factories. OLY is Etherpoly's own ERC-20 in-game currency that can be used to acquire additional cities. Etherpoly cities are ERC-721 NFTs, and exist in limited supply, as the available countries are hard coded into the smart contract. Revenues for your city are influenced by factors such as your city's population, GDP and your existing upgrades.