# How to draw a contour diagram in Mathematica?

This answer at Math.SE contains a neat contour diagram created using Mathematica:

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

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Line, Arrow and Circle inside Graphics; also Point and Text. I imagine the contour was done "by hand", so to speak, inserting appropriate coordinates. –  Michael E2 May 22 '13 at 0:32

Here's a quick 5 minute reproduction of the diagram (I've left the labeling of individual points out):

With[{ε = 0.05, L = 1, thick = AbsoluteThickness[1]},
Graphics[{
thick,
Circle[{0, 0}, ε, {π/2, 3 π/2}],
Arrow[{{0, -ε}, {L, -ε}, {L, -L}, {-L, -L}, {-L, L}, {L, L}, {L, ε}, {0, ε}}],
Text[Style["\!$$\*SubscriptBox[\(C$$, $$n$$]\)", FontSize -> 15], {L/2, 0.1}]
}, Axes -> True, AxesStyle -> thick, Ticks -> False]
]


The key points to make life simple are:

• Use a single Arrow chain for the entire length.
• Use the appropriate definition of Arrowheads to specify the position of the arrow head.
• Use AbsoluteThickness to get a uniform thickness.
• Use the 3 argument form of Circle to draw arcs.
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Graphics[{Circle[{0, 0}, 1, Pi/2 {1, 3}],