Refugio Umbra

"In the shadow of the mountain, deep within Di Ravello's militarized zone, refugees displaced during the construction of the Wall and the burning of the North created a makeshift city in this cave, which soon became a safehaven for rebellion in Insula Striate."

Refugio Umbra is a rebel airbase in Just Cause 3.

Description
This is a Rebellion hideout in Umbra. The hideout has a large hangar (see the picture) and some planes in Rebellion Faction colors and symbols.

You are first introduced to this base after safely landing Rosa Manuela's plane in the mission Rico and the Rose. However, it is possible to come here before the mission if you're traveling around.

The base is a set of Ancient Medici ruins on a mountain and in a cave. One side of the ruins has cliffs and a good view of the area to the east.

Of all the rebel bases, this base has the least number of rooms. Most of the equipment and even beds are in a giant empty space (the hangar), which due to being a cave, must be quite cold. The only rooms as such are Dimah's lab and the revolver training shooting range.