Rockabye Clean Bandit Feat. Sean Paul & Anne-Marie
Capital's found out up to 4 bikes were stolen every single day in Portsmouth last year.
Police reckon up to £500,000 worth was taken during 2011.
Thieves often target bikes as a quick way of making money. Bikes can cost anything from £100 up to £1000.
Police say bike theft is 'rife' in the city, which could be down to Portsmouth being so flat and cycling is an easy way to get around.
Bikes are also popular with the 21,000+ students who live in the city.
Today - Wednesday 4th April - police are holding a special workshop about it where you can get your bike security marked, and buy a D Lock, one of the best ways to secure your bike.
Officers will be at the fountain in Commercial Road between 10am - 4pm.