GOVERNORS ISLAND — Soldiers once stood on the roof of Governors Island's Castle Williams, aiming canons out into the harbor to defend New York against enemy ships.
On Saturday, for the first time in the fort's 200-year history, that same roof will offer panoramic views of Lower Manhattan to its first public visitors, as Castle Williams reopens after $6.1 million in repairs.
"Castle Williams is a real gem and centerpiece for us," said Patti Reilly, the National Park Service's superintendent on Governors Island. "We're very excited about opening weekend."
The historic circular fort has been closed since 2009 while workers restored its leaking roof and crumbling sandstone bricks. Workers also removed lead paint and asbestos and added fire-safety systems, enabling the National Park Service to open Castle Williams' roof and interior spaces to the public for the first time.
"The renovated Castle Williams will be not only another amazing space on Governors Island, but will also give visitors a window into history," said U.S. Rep. Jerrold Nadler, who helped secure funding for the fort's overhaul.
Nadler, Mayor Michael Bloomberg and other local officials announced Castle Williams' opening at a press conference Thursday afternoon.
Starting Saturday, about 600 visitors a day will be able to reserve free timed tickets on Governors Island to see Castle Williams' central courtyard and several refurbished rooms on the ground floor, which are now filled with exhibits about the fort's colorful history as a military base and prison.
About 200 visitors a day will also be able to reserve separate tickets to the fort's 48-foot-high, doughnut-shaped roof, which is accessible by a stone spiral staircase.
The roof — which boasts panoramic views of Lower Manhattan and the Statue of Liberty, along with a Civil War-era canon that could fire a shot as far as Washington Square Park — can only accommodate 15 people at a time.
Castle Williams opened in 1811 to protect New York from an invasion similar to the Revolutionary War, in which the British sailed right into the harbor and occupied the city with ease.
The fort was named for Col. Jonathan Williams, the engineer who designed it. The round structure with vertically stacked canons was radical at the time, when the Army mostly built star-shaped forts, said Michael Shaver, the National Park Service's chief ranger on Governors Island.
"This is not designed to protect anything," Shaver said. "It is designed to inflict serious harm. It's round — there's no corner to hide from."
Castle Williams helped keep New York safe during the War of 1812 but it soon fell into disrepair and became an Army barracks with pigs running around the courtyard, Shaver said. The fort later housed captured Confederate soldiers during the Civil War, and then it became a secure military prison.
When the Coast Guard took over Governors Island in the 1960s, officials considered demolishing Castle Williams, but instead they made it into a community center for the island's families. Each Halloween, the deteriorating fort was transformed into a haunted house.
The new exhibits that go on display at Castle Williams on Saturday use artifacts and descriptions to tell the story of the fort's many lives.
"There's a lot here to take in: human history, design, the location," said Reilly, the National Park Service superintendent. "We hope people come back many, many times to experience the full depth here."
Castle Williams is open to the public from 10:30 a.m. to 4:15 p.m. Saturdays, Sundays and holiday Mondays, with ferries leaving regularly from the Battery Maritime Building, 10 South St.. To reserve free, timed tickets to the fort, visit a white gazebo next to its entrance. The National Park Service will also offer special 15-person tours of Castle Williams and Fort Jay on Wednesdays and Thursdays starting June 13, leaving on the 12:15 p.m. ferry from the Battery Maritime Building. All tickets are reserved on a first-come, first-served basis.