5. @JulianCastro
Followers: 52,742
Bio: “Mayor of San Antonio, Texas, America’s 7th largest city. Keynote Speaker/2012 Democratic National Convention.”
Who is he?: See above. 
Why follow?: Because he’s the boss of San Antonio! Just kidding (… but not really). Castro’s account is more of a tweet aggregation service; his feed largely consists of re-tweets, but they’re re-tweets that shed light on activities and legislation that can shape the city. 
Bonus: Dreamy avatar. Photo: Courtesy