Tuesdays and Thursdays, you can go to the Circuit de Catalunya and make your bike workout there. You have to look on the web that has Bicircuit that day, because sometimes racing cars are training and can not enter.
Admission is 5 €, and can be of 17:30 to 21:00 in winter and 18:30 to 22:00 in summer. There is also a voucher for 25 € with which you can go 8 sessions.
It is a perfect place to train, no cars, no danger .... You can go at your own pace or follow any group to go over there. Every lap is more or less 5km, and is not flat, so you can make a good training!
The experience is incredible to think that there are at real cars and power cycling is incredible. The first time I was there, everything was hallucinating.