If your rowing machine is gathering dust and you are looking for a great workout, I've got one for you. Although I moved to Lisbon in April from the SF bay area, I still row w/my class. Great workouts, several class times available led by rowing coaches. All levels welcome (novice to advanced).
If you don't own a machine and want to, there is a distributor in Lisbon that I just got mine from (good prices, great service--delivered to my door).