To me it looks a bit like a wet and worn out bitumen road after heavy rain.
Most streets built before the early 1900s in NZ were made of macadam, which was highly suitable for horse-drawn vehicles. However, with the rise of motor traffic in the 1920s, many areas had to seek more durable options for road surfacing. The most frequently used material became asphalt or bitumen, which gained widespread use starting in the 1920s.
To me it looks a bit like a wet and worn out bitumen road after heavy rain.
Most streets built before the early 1900s in NZ were made of macadam, which was highly suitable for horse-drawn vehicles. However, with the rise of motor traffic in the 1920s, many areas had to seek more durable options for road surfacing. The most frequently used material became asphalt or bitumen, which gained widespread use starting in the 1920s.
Source: https://teara.govt.nz/en/streets-and-lighting/print