What type of material is the skatepark that looks gray made of?
The skatepark is made of cement.
    src        edge_attr  dst
0     0               in   13
1     2               of   16
2     2  to the right of    8
3     2   to the left of    5
4     2  to the right of   19
..  ...              ...  ...
64   22  to the right of    3
65   22  to the right of   14
66   22  to the right of    5
67   22  to the right of   19
68   22   to the left of   15

[69 rows x 3 columns]