trains  are  so  constructed  that  they 
 have to follow a set path.  this path is 
 called a  "railway",  which is comprised 
 of two metal rails, hence  its nickname. 
 because  the low  friction  between  the 
 wheels  of the train and the rail metal, 
 there  are limits for  how acute a curve 
 can be,  and even more so for  how  much 
 the  ground  under  the  rails  can   be 
 sloped. thus a  railway is often not led 
 on top of hills, rather  through them in 
 tunnels  (if   they   are   large),   or 
            artificial chasms.            
 there will be trees on the side  of  the 
 rails,  but not too  close, or they will 
 be  cut  down by  the  railway janitors. 
 there  will  be  plains, and  bodies  of 
 trains  go by day and  by  night.  along 
      the way, there is information       
 scattered,  often  put on top  of poles, 
 to be  interpreted by the train drivers. 
 different  parts  of  the  railway  have 
         different speed limits.          
 sometimes, trains have to  stop and wait 
 for something to  happen, far away. this 
 is  signaled  by  red  or  green lights. 
 many  people follow  the  rails by foot. 
 often  this  proves to  be  the  shorter 
 path  between  two  points. however this 
 is  frowned   upon,  and  very  impolite 
         toward the train drivers!