Lacking a royal family or a state religion, the US presidency has swelled to fill the void, transforming over the decades into a national personality cult, complete with its own secular temples to these powerful men. The latest pharaonic edifice is about to open on Chicago’s south side, where it looms on the skyline as a towering totem to the 44th president, Barack Obama. He might have seemed humble in office, but in his post-presidential, Netflix-producing afterlife, Obama has erected the largest, costliest and most audacious complex of them all. Behold the $850m Obamalisk – or, as it sometimes feels morbidly like, the Obamausoleum.

Previous presidential libraries have taken many forms, reflecting the values of their creators. Franklin D Roosevelt began the tradition in 1940, building a library in Dutch colonial style alongside his grave in upstate New York, which he hoped would be swarmed with “an appalling number of sightseers”. Since then, every president has followed suit in their quest for immortality, dreaming up ever larger museums and archives, conceived as hallowed places of pilgrimage. Lyndon B Johnson commissioned a brutalist hulk for Austin, Texas, a fitting symbol, its architect Gordon Bunshaft remarked, for “an aggressive … big man”. Ronald Reagan opted for a sprawling California hacienda, with a dedicated hangar for Air Force One, while Bill Clinton conjured a cantilevered metallic box in Arkansas – a literal interpretation of his promise to “build a bridge to the 21st century”.

So, how to symbolise hope, justice, equality and all the other bygone values that Obama championed in his meteoric ascent to the White House? How to commemorate the first Black president in history, in whom so much transformational faith was vested, at a time when so many of his achievements are being relentlessly rolled back?

“We had the idea of a beacon,” says architect Billie Tsien, whose practice, Tod Williams Billie Tsien Architects, won the design competition for the Obama Presidential Center in 2016, on the eve of the first Trump presidency. “We thought of four hands coming together,” she adds, holding her cupped hands up against a colleague’s, as if protecting a flame from the wind.

Above us, sheer walls of granite erupt from the ground at a steep angle, before tapering to form a chiselled 70-metre-high monolith. It looks hewn and cleft, towering over the 19-acre campus like a stocky, truncated obelisk. Rising above the low-rise, low-income neighbourhood, the building has an ominous presence, its mostly windowless heft recalling a menacing sci-fi headquarters, with small chamfered openings suggesting portals from where drones might be launched, or lasers fired. Some have compared it to a flak tower, others to a “Klingon prison”. If it is a beacon of hope, it seems to be one that has been fortified at all costs against the present regime, a defensive bunker to protect its fragile values from siege.

“The president was very, very hands on with the design,” says Tsien, with a rueful air. “He talked a lot about his love of Brâncuși.” That’s the Romanian sculptor who was known for his carved, abstract forms. “And he wanted to make things more angular and cut. To make a form, and then try to work out what goes inside it, is really the opposite of how we’ve worked before. It was a very foreign exercise.”

Obama has spoken of wanting to be an architect, before he chose law, and he clearly relished the chance to wield his conceptual chisel. “When you have a client who says that, you get kind of uncomfortable,” admits Tsien. “It usually means they’ve got big opinions, and he definitely had big opinions. But he was a very good critic.” She says the Obama Foundation, which runs the centre, “wanted something ‘iconic’ which isn’t how we’ve worked before. I don’t think you can design something to be iconic.” Her face falls when we encounter 3D-printed plastic models of the building for sale in the gift shop, priced at $40. Still, the client got what it wanted: this memorable menhir won’t be mistaken for anything else on your mantelpiece.

In the reluctant search for an icon, inspiration also came from a rock that Tsien and Williams acquired on a trip to Ethiopia, of a similar faceted shape to the building, with letterforms carved across its surface. Given that Obama was one of the finest presidential orators since Lincoln, it only seemed fitting to wrap the facade with his words. The lines, from his speech commemorating the 50th anniversary of the marches from Selma to Montgomery, now form a sun-shading screen at the top of the tower’s south-west corner. “YOU ARE AMERICA,” you can just about make out, before the words dissolve into an illegible sea of letters. “I don’t know why it’s in Latin,” one confused local resident told me. The lorem ipsum vibes are real.

The tower is the most visible part of a vast four-building campus, wrought in blocky grey granite volumes, with bronze trimming and concrete interiors, lending the place a rather funereal air. There is a “forum”, housing an auditorium, gift shop, cafe and restaurant (where you can order an Obama burger or Michelle’s family chilli), and a branch of the Chicago Public Library, featuring a presidential reading room of Obama’s favourite books, where you can sit in his favourite Hans Wegner reading chair.

At some points, the Obamamania gets a bit much – there is even an Obama tulip variety in the garden, a gift from the Dutch. Numerous art commissions help to relieve the pervasive greyness, from Mark Bradford’s riotous map of Chicago in the atrium, to Julie Mehretu’s colourful stained glass window, which beams out from the northern facade at night.

The buildings frame a stately granite plaza on one side, while their rears are hunkered into an undulating landscape – designed by Michael Van Valkenburg Associates – that climbs on to their rooftops, including fruit and vegetable planters inspired by Michelle’s garden at the White House. Farther south, past an impressively equipped playground, sledging hill and bowl-shaped great lawn, is Home Court, a shiny aluminium-clad sports pavilion by Moody Nolan, the largest African American owned design firm in the US. It features an indoor NBA-spec basketball court, emblazoned with inspirational Obama-isms, like “Yes we can,” and “No one does big things alone” – a motto the foundation stood by in bringing another architect on board, when Williams and Tsien’s plan got too pricey, with not entirely happy results. The angular metal shed looks like a cheap afterthought, but it will hopefully be a boon for the community.

It faces on to the sledging hill, which was originally to house a subterranean archive, until it was decided that this would be the first presidential library that wasn’t actually a library. (This may be why its official title is the Obama Presidential Center.) To the concern of some historians, Obama’s is the first entirely digital presidential archive, the centre run not by the National Archives, but by his own private foundation, raising concerns over its objectivity. Where once there would have been stacks, there are now 400 parking spaces (despite Obama’s promotion of public transit, this is still the US).

The physical records might not be on site, but the professed aim to transform the presidential library from a scholarly research centre to a bustling hub of community activity is an admirable ambition. “We didn’t build [the centre] to celebrate my ability to bring about change,” Obama declares in a promotional video. “We did it to unlock yours.” It is not just a library, but a “campus dedicated to supporting future change makers”.

The transformational change, he hopes, will happen inside the enigmatic tower where, for $30 a ticket, visitors are transported through four floors of an immersive, interactive Obama experience – a vertical Obamarama. Designed by Ralph Appelbaum Associates, it is an action-packed romp through the couple’s life story, beginning with the civil rights movements that inspired them, their political campaigns, achievements in office, life in the White House, and how you too can “bring change home” (a motto printed on the gift shop bag).

There is also a full-size recreation of the Oval Office, pre-Trump’s Home Depot gilding, where you can stand in line for a selfie at the Resolute desk. Other highlights include campaign memorabilia, from badges to custom Air Jordans, and doll’s house dioramas of various White House rooms – a particularly poignant inclusion, given the mutilation the building is currently enduring. At the preview days, there were boxes of tissues aplenty.

An elevator finally whisks you past a private presidential suite to the “sky room” at the tower’s summit, where panoramic windows frame the city, beneath a momentous white pyramid-shaped ceiling – the pharaonic chamber at last! It was intended to have a celestial quality, with blue words by artist Idris Khan tumbling from the sky. But, in a major blunder, the pyramid doesn’t culminate in a skylight, but a solid white plasterboard ceiling – perhaps an unintended metaphor for barriers that must still be overcome.

From this elevated eyrie, looking out through the big concrete letters, you get a good sense of how the Obama centre fits into the neighbourhood, and why it has been quite so controversial. Down below stretches Jackson Park, laid out in 1871 by Frederick Law Olmsted, designer of New York’s Central Park, part of which was ceded for the presidential complex. The decision to build on a public park sparked furious lawsuits, but the foundation insists that the project has resulted in more parkland and more trees, thanks to the removal of a road. Still, the symbolic land-grab struck a nerve, when there are so many vacant lots nearby.