You may be looking for the first base in the prime version Haven, or the later version, Haven II

Haven II (Light Mobius) was the base of opeations in the Light Mobius universe for the Brotherhood of Guardians prior to the alteration of the timeline. In that universe and by the year 3260, only Spectre, Sojourner, and a vegetative Sabre were known to inhabit it. Knuckles was known to be an infrequent visitor, surprising Sojourner when he arrived to use Haven II's equipment to spy on Rutan, Lien-Da's son. (StH: #134)

It is unknown if Haven II still exists in the altered version if the future, or if it and the Brotherhood were destroyed by King Shadow.
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