I think the designs of the starchitects like Zaha Hadid, Santiago Calatrava, Frank Gehry, Norman Foster, Rem Koolhaas, Daniel Libeskind, Jean Nouvel and Richard Rogers are the most likely candidats.
This will maybe be accompanied by a transnational nomination like "Postmodern globalist architecture".
Some examples:
- Turning Torso in Malmö
- Hearst Tower in New York
- Millau Viaduct
- CMG Headquarters in Beijing
- Reflections at Keppel Bay in Singapore
- Torre Glòries/Agbar in Barcelona
- Bergisel Ski Jump
- Guangzhou Opera House

I also see the architecture that combines urban en natural environments as a possibility, like Singapore's Gardens by the Bay or the Musée du Quai Branly in Paris.

Speaking of the High Line, if you're interested in such projects, my organization is involved with the creation of a 3-mile "Rail Park" (in Philadelphia, on the old Reading Railroad Viaduct built in the 1890s) that would be twice as long and twice as wide as the High Line. Maybe a serial, someday! Phase 1 is just finishing up, so only about 1/4 mile has been finished to date, but it's an ambitious and encouraging project.

https://therailpark.org
http://network.thehighline.org/projects/rail-park/

I mostly think you are right about, tallest, longest, highest... structures. In the long term the Petronas Towers or Taipei 101 are probably not going to have much resonance outside their immediate environs beyond a quirk of "they were once the tallest building in the world".

I think Burj Khalifa may be a bit of an exception to that:
1. For being a massive leap in terms of building height adding over 60% to the previous Tallest Building (which had the advantage of removing all of the niggly little questions about what constitutes a building, do masts and TV towers count etc)
2. I think more significantly, it demonstrates a movement of prestige, resources, focus and capital to the Middle Eastern fossil fuel producing states. Whilst the building itself may not been 100% linked to oil extraction, it demonstrates a refocusing of the global economy on such sites, in much the same way that the Industrial revolution sites in the UK do, even if it is in a secondary way.

For me the Millau Viaduct is significant because it is beautiful. A wonderful elegant solution that used innovative engineering to find a solution to a problem. I hadn't realised it has a superlative attached to it (highest bridge in the world apparently).



Thanks pikkle that looks really interesting. I used to live at various points on North London's similar project, the Parkland Walk, it is was a near essential part of urban life, something we really missed when we moved away from it, so it is great to see similar things happening in other cities, I would happily support a future serial nomination.

Whilst those are post industrial reuse projects in Urban situations we may actually have a rural one being inscribed next year, in the shape of the Hoge Kempen National Park partially created in areas previously used for coal mining and industrial sand quarrying. Depending on how you define such transitions this may qualify, to some extent as a 21st century site, though the transition has been ongoing since the 1990's. So a 20th/ 21st century update of Las Medulas.

Like the spires of Ulm, Rouen, and Cologne Cathedrals, all former "tallest buildings in the world" (only one of which is a WHS anyway and one a rejected T-Lister), I agree that "superlatives" are not grounds for OUV unless it is part of an engineering feat - not simply using the same technology to build taller and taller buildings as in the "spire race" of the late 19th c.

Edit: I think I forgot to delete a repetitive section of my post!

Zaha Hadid's works also come to my mind.

But my sentimental favorite would be the Large Hadron Collider Complex or the LIGO and VIRGO sites. Groundbreaking discoveries made at these sites surely merits OUV. And it would fill the gap or modern scientific heritage too.

Though assessing the impact on integrity of the instrument upgrade will surely be difficult to assess.

The technological and scientific sites of the XXI century are harder to pinpoint. We are just at the beginning of the century, and the discoveries linked to these sites need time to grow, be examined and be made public. Also, scientific research is more difficult to link to one specific site, and often, research is done at universities.

As for specifically built scientific and technological sites, the Large Hadron Collider is, as already cited, one of the more well-known possible future nominations. The LIGO and VIRGO sites mentioned by Zos are interesting too, especially with their link to the discovery of gravitational waves.

Another site that fits this mould might be the Five hundred meter Aperture Spherical Telescope in China, not only because of its size, but also because man used the natural characteristics of the site to build the telescope.