We used connecting pipes to make very large twisty tunnels in the garden today.  We experimented with putting water inside and were trying to work out how to make the water come out of the different pipes.  We found out that we needed to hold one end of the pipe up high to make the water flow.

We also experimented with shouting different sounds through the tubes and really enjoyed listening to the echo as our sounds moved through the pipes.  We might follow this up by making cup phones.