This by itself is a lot of goods, but the reality of it is that you can only really support GE with this GB alone–adding in GBG puts a big strain on it and so the combo effect of Obs is very important. Most committed players will obtain (likely ahead-of-age) Arc and raise it to at least level 80, which will produce 162 of each good for your age for the treasury on every collection. Having all three certainly doesn’t hurt, but the two main ones are Arc and Obs. Reason being is that Arc is very useful and Obs is not only a small footprint, but it’s cheap and useful for its size Atom unfortunately is rather large, and since it’s ME it’s a bit more expensive. Atom is the only one that really isn’t quite worth the space unless you have a major happiness issue you want to fix permanently. Of these three, you will absolutely build Arc because it accelerates everything else, and you’ll want to build Obs in combination.

Obs can be obtained only by earning the blueprints (BPs) from placing on another’s GB in a reward spot or when the BPs are available from an event (or similar), whereas Atom and Arc BPs can be obtained by any typical method available for earning BPs (so aiding/ plundering, placing on a GB reward spot, shrines, etc). Thus far (as of Space Age Asteroid Belt) there are three GBs that will donate to the treasury: Observatory (Obs for short, it has no age), Atomimum (Atom for short, it is from Modern Era or ME), and The Arc (Arc for short, it is from The Future or FE). Sometimes manual donations will still be necessary, but having well-leveled treasury GBs in your guild helps to cut down on how much of that is actually needed, and potentially how often. While you can make manual donations to the treasury by making or trading for goods and then depositing them, it is far easier to build and level up a Great Building (GB) that will donate goods on your behalf. Without it many guild activities come to a screeching halt, and it is easier to drain a treasury than it is to stock it by a long shot. The treasury is what funds things like unlocking levels for Guild Expedition (GE), building things in Battlegrounds (GBG), and more.

It is very important for any guild that participates in guild activities to keep a well-stocked treasury.

The arc in forge of empires