How to match range intervals and one condition between data frames and add values from one to the other data frame

Question

I have two data frames. First, saves coordinates and places

data = [['xx1', 1,10,'Madrid'], ['xx2',15,20,'London']]
df1 = pd.DataFrame(data, columns = ['precode', 'start', 'stop','city'])

The second

data2 = [['xx1', 3,11,'location1',], ['xx2',9,17,'location2'],['xx2',21,30,'location3'],['xx5',1,19,'location4']]
df2 = pd.DataFrame(data2, columns = ['precode', 'start', 'stop','locations'],)

I want to check if locations are in city. If so add in df2 the name of the cities

precode  start   stop     location       city
xx1      3       11       location1      Madrid
xx2      9       17       location2      Madrid;London # If more than one city affected, add as many as cities affected as found
xx2      21      30       location3      NaN   
xx5      1       19       location4      NaN

I don't even know how to start. Shall I convert column into a dict to do the checking process or can shall I itinerate values of one column to the column of the other data frame. df1 is much bigger than df2. Both data frames have more columns. The final output need to be an identical as was df2 but with the new column city.