Biking

There are many bike paths in Poland, all you have to do in see the painted red with the bikes on the sides on the sidewalks, or you could always bike on the streets, although most people don't do that unless they are training for a marathon or if there are no sidewalks at all.

All of the bike paths take you to different places, and they could take you to anywhere. This is also a famous way of transportation to anywhere. Many people, in the summer, take their bikes to work and bike. But you could always see many people riding their bikes to get somewhere in the summer.

If you are going to use your bike frequently, it is said that you have to get some special kind of license so the police and everyone know that you are a safe biker and you are not a harm to yourself or others (yes, there are police who stop bikers for certain things)
Note: I don't know if this is true or not, you will have to ask your friends or ask people at the Embassy to see if it is true and how to get one of these licenses if you are planning on using your bike frequently to get the places you need to go.

There are many places to go mountain biking if you want some excersize or just for fun on the weekends/summers. Here are some of the places to go mountain biking:

If you want to go easy, you can take these paths:
Gdansk-Gorki-Westerplatte
15.01 miles
near Plonia Mala, Gdansk

Source and stones circle
8.03 miles
near Bartodzieje Wielkie, Województwo kujawsko-pomorskie

Pruszkow
11.72 miles
near Piastów, Województwo mazowieckie

For more difficult paths you can take these ones:
From Lebork to Wejherowo
62.31 miles

near Lębork, Województwo pomorskie

cracovia-ustron

80.67 miles

near Śródmieście, Województwo małopolskie

Of course these are only some of the bike trails in Poland, if you want to see more, you can go to this website, where there are many many more bike trails listed:

http://en.wikiloc.com/trails/mountain-biking/poland