The Algonquin Municipal Building is a highrise office building owned by the Liberty City government in Grand Theft Auto IV. Based on the Manhattan Muicipal Building in New York City, the only role the building plays in the game is that it houses a stunt jump inside the tower's base.
The Tower's Tunnel
The tower's tunnel which in real life once had vehicle traffic, is possibly closed in the game due to safety precautions against terrorism (possibly the same reasons that all the bridges were closed at the beginning of the game. That may be a reference to the mission in GTA LCS Toni puts a bomb in the subway tunnel and the whole Fort Staunton neighborhood explodes). The real life building is home to many public agencies.