Some people pray at any place such as foot path, a courtyard or an open field.
Some do not even use a prayer mat or any sheet of cloth or paper, although these places may not be all that clean. This is a reference to the fact that a Muslim may pray anywhere provided that the place is free of impurity. It also refers to the fact that purification is achieved through dry ablution. Therefore, it is perfectly permissible to offer prayers in the sort of places you have mentioned, provided that we make sure that there is no impurity where we pray. It is perfectly acceptable that we offer prayers on the pavement, by the side of the road, in a field or a garden or anywhere else.