[@GrafRoy Zeppeli]

Ah well the Other Place isn't really a physical thing that you can touch. The other place is all made up of the essence of the world, every being living their just constantly moving around as their purest form, swirling and being ripped apart and pieced back together almost constantly. When a foreign being comes into the Other Place and tries to settle some sort of order in the chaos (such as imagining its body or any physical thing found in real-world), the being would be destroyed or sent back by demons for even reminding them of their slavery in real-world. If not, they would be turned into mush as the spirits their are something between solid and liquid. 

For a more accurate description, go to the wiki.
http://bartimaeus.wikia.com/wiki/The_Other_Place