Lahti is a city in southern Finland, a bit over 100km away from the country's capital, Helsinki. Located on the shores of Vesijärvi (Water Lake), the city has just over 100,000 people, which makes it the 9th most populous city in Finland. Although there are hostels in Lahti and tourism, it is mostly industrial city.
Lahti doesn't have it's own airport, but it is served with a very good network of buses and trains that you can use to get to and from your Lahti hostel. It resides just on the side of expressway 4, also referred to as the Lahti Highway. This is a good option to get around if you want to visit Helsinki and have a car. There is also a very functional public transportation system in the city, and the tickets are reasonably priced.
Lahti hostels fall to the same category as most hostels in Finland: good value, but a bit on the expensive side. Hostels in Lahti often arrange many activities you can book through them, and this might be a good way to experience the city and the surrounding areas for the first time.
Maybe the most known thing to see in Lahti is the Sibelius Hall. Built in honor of the late Finnish composer, Jean Sibelius, the Sibelius Hall is one of the largest wooden buildings in Finland. There are guided tours to see the building, and it contains many places of interest. There are also events and concerts in the Hall during the whole year (see their website for further details). There is also a very nice park and a great city train called "Puksu" which you can take to see many interesting parts of the city.