In the world of celebrity real estate, tree houses seem to be the latest fad. And it’s not the simple backyard ones made of ply woods that have attracted the fancy of some high-profile celebrities.

These tree houses are fancy and are the ultimate when it comes to luxury, even if it is being constructed for children.

For instance, Harry Potter franchise author J K Rowling was recently granted permission by the City of Edinburgh Council to build such two tree houses in her backyard. These Hogwarts-style two-storey tree houses will cost her an estimated $404,300 and is being built for her two sons – David, nine, and Kenzie, seven - the Guardian reported.

According to the paper, the tree houses will feature turreted windows, pennants, a basket and pulley, and an owl perch.

While one of the tree houses will have a long tunnel under a walkway and a fireman's pole, the other will feature a trapdoor, rope ladder, a metal slide and spiral staircase down to the garden, the Guardian report said.

Meanwhile, designers and architects say that the tree house craze is spreading like wildfire among adults, too.

"After I built a tree house for Sting in Tuscany, Donna Karan hired me to create two tree houses for her grandkids. Donna talked to Julianne Moore, who wanted one. Then Julianne introduced me to Val Kilmer, who wanted one, too," Roderick Romero, a Manhattan designer told Forbes.

So what’s the specialty of these tree houses? "People think 'tree house' and imagine creaky plywood forts where kids sneak away to have their first kiss," said Romero, adding that it has moved beyond that.

Most of these luxury tree houses boost all the fine, attractive qualities of trophy houses with posh furniture, French windows, sliding doors, chef’s kitchen and air conditioning. And it can set back the owner by a minimum of $1million, depending on the clients’ imagination and budget.

"One client wanted to hit golf balls from his tree terrace, so he had us design a tee platform with removable railings,” Andreas Wenning of Baumraum told Forbes.