The gorgeous gothic tower looking over Riverside Church had been closed to the public for two decades.

The tower is the tallest steeple in North America, looming 392 feet over Morningside Heights, the Hudson River and Grant’s Tomb, with a bird’s-eye view of Columbia University and an uptown survey of Manhattan skyscrapers. About two years ago, the current church administration started to wonder what it would take to reopen the tower.

The problem? No one could figure out why it closed in the first place. The story within the stained-glass-adorned walls and arched, brick halls of the church went that it shuttered after Sept. 11 over security fears. But no church records existed that explained why it closed; the Department of Buildings and other city agencies had no record of stepping in to close it, either.

“A lot of that remains a mystery,” says Brian Simpson, the church’s director of communications. “Once we went down that path, there weren’t a lot of roadblocks.”

So, after its unexplained hibernation, the tower finally opened for tours again in December. It didn’t even need any repairs, Simpson says.

For a $25 ticket, you can take an elevator up 20 floors and then walk the 145 stairs to reach the top. Once there, you’re greeted with open-air, arched limestone windows offering stunning views.

On the north side, the view includes the George Washington Bridge and Harlem; move over to the east side and you can see The Bronx, including Yankee Stadium, Randalls Island and the edge of Queens. Look south for a panoramic view of the Manhattan skyscrapers rising from the city, with One World Trade Center peeking out in the distance.

“When it’s really warm, this is really a sanctuary,” says Raymond Rodriguez, the tower tour guide who has worked at the church for 28 years. He compared it to the labyrinth inlaid on the floor of the church’s sanctuary that parishioners can walk to find peace. “You come here and meditate. Some people have the labyrinth, I have here.”

The climb up has distinct Quasimodo vibes: You grab a handrail as you cross metal scaffolding weaving between a nest of 74 bells tinged green with age, including a massive 20-ton bell the church says is the largest tuned bell in the world; the smaller bells above are just 10 pounds. When the bells ring every 15 minutes, the jarring bong shakes the scaffolding slightly, although the platform is sound.

A side room near the bells houses the carillon, the instrument used to play the bells, which looks like an organ crossed with a weaving loom. The carillonneur, as the person who plays its many pedals and levers is called, is a highly skilled musician, Rodriguez says.

The rest of the church itself is as impressive and historic as the tower: Built in 1930 by John D. Rockefeller Jr. and modeled after a 13th-century cathedral in Chartres, France, it quickly became an interfaith and interdenominational facility that welcomed all. Martin Luther King Jr. gave sermons there on five occasions; Kareem Abdul-Jabbar (then Lew Alcindor) played basketball in its youth league. Visitors to the church and its 2,100-seat sanctuary are met with pride flags, Black Lives Matter signs and stained glass so intricate it’s almost psychedelic.

The middle of the tower’s top floor now is a junk-filled workshop, but years ago it was used for events, and the occasional wedding proposal. The church hopes to soon turn it into a cafe or event space, so people can linger near the stunning views.

“Eventually, people can just come and hang out, have some coffee — a drink maybe,” Rodriguez says before joking: “Hopefully, they won’t fall out.”

490 Riverside Drive, between 120th and 122nd streets; TRCNYC.org. The 90-minute tower tours run Wednesday to Saturday at 1 p.m. Tickets are $25.