Of course! That's the whole idea, to experience every corner of the city on your bike. Just make sure you lock the bike when you take breaks. You don't need to park the bike at our hubs during your rental.
Some cities may have designated bike racks where bike parking is legal, e.g. the city of Amsterdam may remove bikes that are not in those areas. Please look out for bike parking signs on the streets or simply ask a local to make friends!