The 4,500 year old ruins of a once-hidden ancient civilization in Pakistan are being threatened by the country's historic rains

• Some of the walls of Mohenjo-Daro have been destroyed as a result of Pakistan's historic flooding.
• The Cultural, Tourism, Antiquities, and Archives Department of the Sindh province estimated that repairs would cost $45 million.

A preserved ancient city in Pakistan has witnessed "mass destruction" as a result of the country's historic rains and could cost millions of dollars to repair.

Ahsan Abbasi, a curator at Mohenjo Daro, told the Associated Press the outer walls of the city had been damaged by the rains.

The Mohenjo Daro's "Buddhist stupa" — a religious burial ground — survived the rains, however. Repairs to preserve the World Heritage site are now underway, Abbasi told the AP.

Mohenjo Daro — or Mound of the Dead in Sindhi —is an ancient civilization in the heart of Pakistan that cropped up on the Indus river 4,500 years ago. The ruins of the city are now a UNESCO world heritage site.

Mojenjo Daro was discovered in the 1920s after mysteriously disappearing 4,000 years ago, according to National Geographic. Remnants of the city include bronze statues, pottery and a pool called the Great Bath.

The immaculately planned city, with endless rows of baked brick walls, was considered the "first great urban center" of the Indus Valley civilization and had complex drainage systems to address ancient floods, according to UNESCO.

The Indus Valley civilization is one of the world's earliest civilizations, lasting between 2500 and 1700 BCE, and consisted of over 100 towns and villages along the Indus river in modern-day Pakistan.

A letter sent to UNESCO by the Cultural, Tourism, Antiquities, and Archives Department of the Sindh province said the Indus Valley civilization site had seen "mass destruction" and requested $45 million for repairs, according to CNN.

During UN Secretary General António Guterres' visit to the country on Friday, UNESCO responded with $350,000 in funds to help rebuild the site, as well as other destroyed sites across the country. The money will help to address crucial repairs while UNESCO continues to assess the situation, CNN reported.

The letter also said that various parts of the site and the museum were given to people to take refuge during the monsoon.

Over the last two months, Pakistan has endured heavy monsoon rains and glacier melts that have submerged one-third of the country and impacted 33 million Pakistanis. Over 1,100 people have died so far.

The Sindh province, where Mohenjo Daro is located, has been one of the worst hit by the flooding due to its location near the overflowing Lake Manchar.