This article (the first of two) contains ideas for investigations. Space-time, the curvature of space and topology are introduced with some fascinating problems to explore.
Lyndon Baker describes how the Mobius strip and Euler's law can introduce pupils to the idea of topology.

It might seem impossible but it is possible. How can you cut a playing card to make a hole big enough to walk through?
This is the second of two articles and discusses problems relating to the curvature of space, shortest distances on surfaces, triangulations of surfaces and representation by graphs.

If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable. Decide which of these diagrams are traversable.
This article looks at the importance in mathematics of representing places and spaces mathematics. Many famous mathematicians have spent time working on problems that involve moving and. . . .
The tangles created by the twists and turns of the Conway rope trick are surprisingly symmetrical. Here's why!

Euler discussed whether or not it was possible to stroll around Koenigsberg crossing each of its seven bridges exactly once. Experiment with different numbers of islands and bridges.
Here is a proof of Euler's formula in the plane and on a sphere together with projects to explore cases of the formula for a polygon with holes, for the torus and other solids with holes and the. . . .
Did you know that ancient traditional mazes often tell a story? Remembering the story helps you to draw the maze.
A personal investigation of Conway's Rational Tangles. What were the interesting questions that needed to be asked, and where did they lead?

Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
There is a long tradition of creating mazes throughout history and across the world. This article gives details of mazes you can visit and those that you can tackle on paper.

This problem is about investigating whether it is possible to start at one vertex of a platonic solid and visit every other vertex once only– returning to the vertex you started at.

A Hamiltonian circuit is a continuous path in a graph that passes through each of the vertices exactly once and returns to the start. How many Hamiltonian circuits can you find in these graphs?