The 1991 Protocol on Environmental Protection to the Antarctic Treaty is one of the key international instruments guiding human engagement with Antarctica. This article focuses on some of the key legal and practical aspects of the implementation of the Protocol for the past three decades, as seen from the perspective of an observer active in Antarctica and in Antarctic Treaty System decision-making bodies during this period. An “Antarctic time traveller” travelling between 1991 and 2021 and back would recognise the continuity and change prevalent in Antarctica and its governance regime. The lasting legacy of the Protocol includes its objective, designation and environmental principles, as well as the mining ban and all related content. However, the future prospects of the Protocol depend on the Parties’ ability to keep it relevant in a changing world while maintaining their original vision of comprehensive protection of the Antarctic environment and dependent and associated ecosystems. The challenge for Antarctic Treaty actors for the next decade and beyond will be to reaffirm the grand vision of the Protocol while addressing tensions between common interests and national interests, and pervasive global change.