How to install a very big map?

I'd like to install a very very big map, it being of my country. I don't wanna install multiple smaller maps and connect them to make some good connections, as that'll be time consuming. so, how do I install a a very big map? The map would be around 1000km x 1000km and detailed. Even if it'd take me 100GB to install it, where could I get it from?