It's also the launching point for the Seven Mile Bridge, often referred to as the 8th Wonder of the World. The bridge drops you onto Big Pine Key and Bahia Honda State Park. The former is great for fishing and the latter is where you'll find one of America's best beaches.
Yes. You'll need to obtain approval no less than 72 hours prior to travel to the US via the ESTA (Electronic System for Travel Authorisation (ESTA) scheme.
From Miami, Key Largo is 55 miles, Islamorada is 72 miles, Duck Key is 100 miles, Key Vaca is 104 miles and Key West is 160 miles. Locations in the Keys can be pinpointed by the use of 'mile markers', which denote the distance in miles from Key West.