Isaiah 2:2. “And it shall come to pass in the last days, that the mountains of the Lord’s house shall be established in the top of the mountains, and shall be exalted above the hills: and all nations shall flow unto it.”
This verse clarifies that what Isaiah is seeing is a vision of the “last days,” something in the far future, the glory of the Millenial Kingdom.
Apparently, the Temple in Jerusalem will have a much higher situation than before. It is indicative of the domination that the Lord will have over all the nations (Psalm. 76:4-5).
“All nations shall flow flow unto it.” Picture the tumult of the nations today, fighting and striving like a storm on a raging ocean. During the Kingdom, there will be peace. The people of all nations will flow like a quiet river to the place where Jesus reigns. Mount Zion and the Lord’s House will see a constant gathering of the people of all nations as they recognize Who He is.