The Dengineers build 11-year-old Ben a camouflaged adventure bunker.
Sibling rockers Sami, 9, and Nadia, 12, need their own soundproofed rehearsal room.
A massive Manchester United fan, 10-year-old Billy is in need of a football den.
Ella wants a den to escape the 35 bikes that are kept in every room of the house.
Jazz and Katelyn love dancing and want to put a dance studio in Jazz's mum's cellar.
Eleven-year-old Nathan wants a kitchen hangout, where he can practise being a chef.
Nyobi needs room, a desk space and art materials, for her design projects.
Ten-year-old Ben wants a den with enough room for his beloved train set.
Sienna really needs a new bedroom which can double up as a spy den, with lots of gadgets.
The pupils of the Lancasterian School want an exciting space that everyone can hang out in.
The presenters look back at all the dens they have built throughout the series and reminisce about the great kids, the tense surprises and the big reveals.