What is located on top of the building?
The clock is on top of the building.
    src        edge_attr  dst
0     1  to the right of    2
1     2   to the left of    1
2     2  to the right of   13
3     3   to the left of   14
4     3   to the left of   15
5     3  to the right of    8
6     4  to the right of    7
7     5           behind   13
8     5           behind    7
9     5           behind   15
10    5           behind   14
11    6               on    7
12    7   to the left of    4
13    7      in front of    5
14    8   to the left of    3
15    9               on    5
16    9        on top of    5
17   10               in   11
18   13   to the left of    2
19   13  to the right of   15
20   13  to the right of   14
21   14  to the right of    3
22   14   to the left of   13
23   14  to the right of   15
24   15   to the left of   13
25   15   to the left of   14
26   15  to the right of    3