Question: [This answer](https://math.stackexchange.com/a/393125/19661) at Math.SE contains a neat contour diagram created using Mathematica:
![](https://i.stack.imgur.com/Jb3i2.png)

What Mathematica functions I can use to draw diagrams like this?

Answer: 
```
Graphics[{Circle[{0, 0}, 1, Pi/2 {1, 3}], 
           Arrow[{{10, 1}, {0, 1}}], 
            Line[{{0, 1}, {10, 1}, {10, 10}, {-10, 10}, {-10, -10}, {10, -10}, {10, -1}, {0, -1}}]},
         Axes -> True, Ticks -> None]

```

![enter image description here](https://i.stack.imgur.com/1ZT1Y.png)
One can use `Arrow` as following.

```
pts = {{0, -1}, {10, -1}, {10, -10}, {-10, -10}, {-10, 10}, {10, 10}, {10, 1}};
Graphics[{Circle[{0, 0}, 1, Pi/2 {1, 3}], Arrowheads[{0, 0.03, 0}], 
  Arrow[{{10, 1}, {0, 1}}], Arrow[Partition[pts, 2, 1]]}, 
 Axes -> True, AxesStyle -> AbsoluteThickness@1, Ticks -> None]

```

[![enter image description here](https://i.stack.imgur.com/U0IMQ.png)](https://i.stack.imgur.com/U0IMQ.png)

And replace `Arrowheads[{0, 0.03, 0}]` to `Arrowheads[{0, 0.03, 0.03, 0}]` to get

[![enter image description here](https://i.stack.imgur.com/iS5Lp.png)](https://i.stack.imgur.com/iS5Lp.png)