What are some ruined tourist attractions you can no longer visit?

Read Peter Wade's answer to What are some ruined tourist attractions you can no longer visit? on Quora

Far too many tourist attractions are being slowly and irreversibly damaged. Our admiration and appreciation for priceless artifacts, ancient structures, and historic sites lures many of us for a visit. But our curiosity is actually having a negative impact on their preservation.

Some, like Machu Picchu, are irreparably altered by the sheer number of pedestrians. Others, like Spain’s Cave of Altamira, are damaged by mere human breath. And some, like the Great Barrier Reef, are being decimated by climate change.

Most of these sites will continue to survive, for now. The worst cases have led to temporary closures because of excessive tourist usage, like Maya Bay in Thailand and Boracay in the Philippines. But they’ll eventually recover and be reopen.

But you’re wondering about attractions that have been completely ruined to such an extent that we can no longer visit them. Indeed, there are a small handful of attractions that fall into this category:

Guaira Falls, Brazil-Paraguay border-

This massive valley of countless waterfalls was one of the most spectacular in the world and a popular tourist destination in South America!

In 1982, both Brazil and Paraguay agreed to destroy the waterfalls during construction of the Itaipu Dam. The valley was flooded by an artificial lake and now looks like this.

World Trade Center, New York City, New York-

During the 1990s, the World Trade Center twin towers welcomed 200,000 visitors daily. The rooftop of the South Tower was my personal favorite observation deck in the entire world. I’ve been to most of the notable observation decks, but there was nothing like this one!

Both buildings were destroyed on September 11, 2001, by cowardly terrorists.

Nohmul Pyramid, Belize-

This was a mighty Mayan pyramid that stood for 2,300 years. But it was no match for a bunch of corrupt businessmen.

On May 13, 2013, De-Mar’s Stone Company inexplicably destroyed 70% of the pyramid, utilizing the stone for other construction projects.

El Paraiso, Peru-

The remnants of a 5,000-year-old pyramid, the oldest in the Western Hemisphere, once stood amidst the El Paraiso archaeological site north of Lima, Peru.

In June of 2013, developers destroyed this pyramid, then attempted to hide their sins by burying the site in trash and setting it on fire. Police stopped the group before they destroyed the other 11 pyramids.

Duckbill, Pacific City, Oregon-

Along the gorgeous Oregon coastline, a rock formation that literally looked like a duckbill (although I see an ostrich head) served as a cool photo op for tourists for over half a century.

In 2016, a group of vandals completely toppled the outcropping. Despite being caught on film, they have never been found or prosecuted.

Temple of Bel, Palmyra, Syria-

This mighty complex was dedicated in AD 32 and utilized for religious services until the 1920s. The magnificent grounds became a UNESCO world heritage site.

On August 30, 2015, the terrorist group ISIL blew up the temple for malicious reasons, ending its nearly 2,000-year existence.

In fact, between June of 2014 and June of 2017, ISIL destroyed at least 14 shrines and tombs, 11 mosques, 9 churches, and 3 monasteries in the Middle East. This included the Imam Awn al-Din shrine, one of the few structures to survive the 13th-century Mongol invasion, and the Great Mosque of al-Nuri with its famed leaning minaret.