You can make a lot of interesting hamster tube runs with vertical tubes, especially if you can place them outside the hamster cage. (choosehamstercages.com)
Keep in mind that dwarf hamsters may have trouble climbing up tall vertical tubes. (choosehamstercages.com)
The Biocoil is a transparent vertical tube — around 5 metres high - through which the algae are constantly circulated in a nutrient broth. (newscientist.com)