Races are first unlocked after the memory ‘Nightcap’ in DNA Sequence 1. You can locate them on your map by pinpointing a icon. There are six Races available to you throughout the game. Completing just one will unlock this achievement.
The first available race in Florence is called ‘Florentine Sprint’. There is a icon near the Palazzo della Signoria, south-southeast of The Duomo. Locate a man glowing white in the northwest corner of the plaza and press to speak with him. He will challenge you to beat his time in a race. Accept the mission and the timer will start. You will have 1:30 to finish the race. Races are a test of your ability to jump and climb on buildings and rooftops. Follow the yellow crosshairs on your mini-map to your destination. If you finish before the time expires, the achievement will unlock.