At the southern tip of Finland, Turku lies at the end of the mainland before the beginning of a large archipelago of islands, across from Sweden. A great way to see the city is the Jakke River Ferry. It tours along the Aurajoki River which is central and also includes a tour on a small train to give you an all rounded circuit. Given its location, Turku is a hub for smaller towns based just outside it and so it sees a lot of external visitors, especially due to the port that connects it to Sweden. If you're hiring a car in Turku, then just outside the centre are the Virnamäenpuisto and the Nummenranta parks, both based along the main river they are the ideal place to spend the day at with a picnic.
History is a serious element for any trip to Turku, the city library and Turku Castle are both well worth a visit. The Turku Cathedral is a great piece of local architecture and is the shrine for the whole country. There are several notable people, native to Sweden and Finland buried in the cathedral. If you are hiring a car in Turku, take time to visit the Aboa Vetus. The museum is home to the medieval streets of the city, taking you underground to see the artefacts that are still being uncovered today. With the surrounding waters, the Forum Marinum has a range of anchored museum ships to compliment the interior exhibits.