ELI5 Sister Cities - are twin cities a gimmick or is there more to the relationship?

Which US city has a 4 block area nearly identical to its sister city of Seville, Spain? Are twin cities a gimmick or is there more to the relationship? Where did the concept start? What's the most boring sister city combo?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community as always and in particular the following users whose questions and comments formed the basis of this discussion: conroybeckett, tardis98, snowlizzard, oliverthewanderer, thedankbank1021, kikob, peacewing, imgray & sagec_random12 To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: [email protected]