The torus:

This is obtained by identifying the opposite sides of the square $I^2$ according to the following scheme. For each $x \in [0, 1]$, the pair of points $(x, 0)$ and $(x, 1)$ are identified. Likewise for each $y \in [0, 1]$ the pair of points $(0, y)$ and $(1, y)$ are identified. One first obtains a cylinder $S^1 \times [0, 1]$ which is then ``bent around'' and the circular ends are glued together. One obtains a space which looks like the crust of a dough-nut (or medu vada).