Without more detail, it’s hard to tell…guesses so far include the Houses of Healing, and two votes for the court in Minas Tirith with the remains of the White Tree. From Stevanos:

“My guess for the new set is that it will be the garden outside the White Tower of Ecthelion atop Minas Tirith. The wall is part of the Tower, and the hole is where the (Dead) White Tree will go. It will also make a symbolic backdrop for the romance of Faramir and Eowyn – and especially when the new White Tree is planted.”

All the details we have so far are here