Mäkelänrinne Swimhall is one of the best swimming-halls in Helsinki, if not the best. It's quite big, with four to six different-sized pools with different functions - for kids, for therapy, for jumping and for more or less serious condition or competition swimming; there are even areas for water aerobics and hydro running; there's no jacuzzi in itself but there are bubbles in the therapy pool! The location is excellent, and you can easily get there by car, public transport and bike. The price is quite reasonable for first-class swimming, just a few euros per adult. There are Finnish saunas and a steam bath, and even a cold water pool for the extremists. The swim hall is very spacious, has huge windows letting in daylight, and there's usually good space for swimming.
If you also want another type of workout, there's a gym too. A cafeteria is also available, and they offer lunch and pastries and sweets etc. This is a great place for anyone who likes a good swim!