To get to this location, you must use a flying character, an air vehicle, or a water vehicle. The Remote Terminal at this location is located on the area's dock. It is locked with a gold lock, so you will have to destroy it using a heat character. This one is a Remote Terminal for water vehicles.
After activating the Remote Terminal, you can find this character on the roof of the Gotham Observatory. Go to the left of the Remote Terminal and then right to find a bat symbol. Use a character with a Grappling Hook to reach the high walkway, and scale a wall. Then continue forward from the highest walkway to reach the roof of the Gotham Observatory and confront this character. In his boss fight, he will hide underground and five Freeze Goons will come to attack you. Defeat them to return Mister Freeze to dry land. When he returns to solid ground, he will use stomp attacks to create shockwaves and use his Freeze Gun to freeze you. If he freezes you, move quickly to thaw out. Hit him quickly to remove a heart. When you take a heart from him, he will return underground and eight Mr. Freeze Goons will attack you. Defeat them and remove another heart from Mister Freeze to return underground. Defeat ten more Mr. Freeze Goons and remove Mister Freeze's last heart to defeat him. When you remove his three hearts, you can buy him for 500,000 studs.
Use a flying and laser character to destroy a gold plate on the tip of the Gotham Observatory telescope and reveal this Gold Brick.
To the left of the bat symbol on the Gotham Observatory dock, you will find a black box. Use Lex Luthor's Deconstructor to deconstruct it and reveal this Gold Brick.
When you are using the Remote Terminal, choose one of the water vehicles and board one of them to navigate through buoys. Complete a water race passing through buoys to get this Gold Brick.