Anton's Seeds of Safe Haven

A 15-foot-radius, 45-foot-tall immobile gazebo made from tree trunks, branches, leaves and vines will burst out of the ground, centered on a sapling that sprouts from where the spell was originally cast. The spell will fail if anything bars the gazebo's growth while it forms.

Creatures and objects within the structure when the spell is activated can enter or leave freely. All other creatures and objects are barred from entering. Spells and other magical effects can't extend through the gazebo or be cast through it. The atmosphere inside the structure is comfortable and dry, regardless of the weather outside.

Nine creatures of Medium size or five Medium and one Large size can fit inside with you. 

The structure is visible from the outside, but will appear empty even if occupied by creatures or objects. The spell ends if the soil is removed or the central sapling is tampered with (in which case, the entire structure withers and turns to dust).