When Mark Doty ran across a collection of 35mm slides that had been sitting in city of Dallas storage for decades, he had no idea if the scans would turn up anything interesting.

They most definitely did — including old construction photos of City Hall, the iconic building designed by architect I.M. Pei.

Doty, the Dallas Historic Preservation's chief planner, had unearthed a trove of original images of downtown Dallas area streetscapes and skyscrapers dating from the 1970s through the early '90s.

Dallas Historic Preservation is letting KERA show a few of our favorites from the collection, which you can view in full on the department's Flickr account. (The preservation folks have a few favorites, too — take a look at them in senior planner Jennifer Anderson's blog post.)

We've included dates where they're known; not all slides were marked.

Dallas City Hall, 1500 Marilla

Credit City of Dallas Historic Preservation Dallas City Hall construction, 1974

President John F. Kennedy was assassinated on Elm Street in 1963. Then businessman Jack Ruby shot suspect Lee Harvey Oswald in the basement of the Municipal Building. In the following years, Dallas came to be known as "the City of Hate."

City leaders resented that label. Part of the plan to turn that reputation around was a new municipal building: Dallas City Hall. Famed architect Pei — responsible for works like the pyramid at the Louvre in Paris, the John F. Kennedy Library in Boston and Dallas' Morton Meyerson Center — was chosen for the project, and construction began in 1972.

The modernist building was completed in 1978. It sits at 1500 Marilla St., next to the Kay Bailey Hutchison Convention Center on the south side of downtown, visible on busy Young Street.

Below is what the area looks like now using Google Street View. To explore City Hall's surroundings, use your cursor or finger to move the 360-degree image around. Tap the white arrows to move up and down the street and to turn corners:

Awalt Building, West End

Credit City of Dallas Historic Preservation Awalt Building, built in 1905

For several years this building was probably best known to downtown-dwellers as home of the West End Chipotle, before that restaurant location closed. But long before that, the 114-year-old Awalt Building operated as a furniture warehouse for decades. Now it's at the heart of the city's historic West End district, on Market and Pacific streets, near the DART West End station.

The building was headed for the wrecking ball to make way for a parking lot before it was rescued in the 1990s.

Here it is today:

Hart Furniture building, Elm and Harwood

Credit City of Dallas Historic Preservation The Hart Furniture store, date unknown

This is one of downtown Dallas' oldest structures, opening in 1888. It housed the Hart Furniture store for much of its life before shutting down in 1991 after 77 years in business. Located on the corner of Elm and Harwood, the building's next-door neighbor is the equally historic Majestic Theatre.

Exterior renovation in recent years included paint removal, revealing the Italianate-style building's original red brick.

Here it is today:

Cathedral Shrine of the Virgin of Guadalupe, Pearl and Ross

This November 1979 slide below shows a couple of different points of interest within downtown's Arts District. Let's take a look.

Credit City of Dallas Historic Preservation Cathedral of the Virgin of Guadalupe, left, November 1979

The cathedral on the left side of the photo opened in 1902, but its true history goes even further back.

It was established as Sacred Heart Church in 1869. A few years later, its first official building opened on Bryan and Ervay streets. When it outgrew that modest structure, the cathedral was built on its current spot, on Ross Avenue and Pearl Street. The Cathedral of the Sacred Heart was dedicated in 1902.

In the 1970s, Sacred Heart and Our Lady of Guadalupe on Harwood Street merged, and the combined congregation made Sacred Heart its home. Then in 1975, Sacred Heart was renamed Cathedral Santuario de Guadalupe — the Cathedral Shrine of Our Lady of Guadalupe, who is the patroness of the Americas and a prominent religious figure in Mexican identity.

In the background of the photo, you can see two towers in the middle of construction. The tower being built on the left is the JPMorgan Chase Tower. The 55-story postmodern skyscraper is the fourth-tallest building in the city and helps define Dallas' distinctive skyline. The tower under construction on the right is the 2100 Ross Avenue building. The two towers are connected by a skywalk.

Here is what the streetscape looks like today:

Bonus: Here's a photo from Instagram that shows the cathedral from the front.

Old Red Museum of Dallas County History & Culture, Houston and Main

The date of this photo of the Old Red Museum of Dallas County History & Culture — formerly Dallas County's courthouse — is unknown. Besides the tint, there's a big difference between this vintage picture and the Street View image below it. Can you spot it?

Credit City of Dallas Historic Preservation Old Red Courthouse

... See it yet? ...

It's the https://youtu.be/posltL_Zh-E" target="_blank">clock tower! The Romanesque red sandstone building was constructed in the 1890s with a clock tower, but officials removed it in 1919 after discovering major structural issues, afraid it might collapse in on the courthouse. It wasn't until 2007 that a reconstructed tower and clock were built back onto the top of Old Red. The building is now a museum, and its latest construction project is a new roof.

The Magnolia/Mobil Oil Pegasus

This is a tale of two Pegasuses (or, depending on your source material, Pegasi).

Credit City of Dallas Historic Preservation A red neon Pegasus was placed on top of the Magnolia Oil building, now the Magnolia Hotel, in 1934. Photo date unknown, but it's sometime in the latter part of the 20th century.

In 1934, a rotating, porcelain-and-neon flying horse was perched on top of the Magnolia Oil headquarters on Commerce and Akard streets. It was the tallest building west of the Mississippi River for some time, and the pegasus was its crown. Mobil Oil absorbed Magnolia in 1959, and Mobil took on the red Pegasus as its own logo. It was one of the most iconic corporate symbols of the 20th century.

Fast forward to the '90s when the building became the Magnolia Hotel. The weathered, rusted Pegasus was replaced with a brand new one in 2000.

For about 12 years, the original horse sat forgotten in a shed, even going missing for a while. When it was finally found, it was restored and mounted on a miniature oil derrick-like stand. It's lived on the lawn of the Omni Dallas Hotel in downtown since 2015.

Today, the city and its residents have adopted the Pegasus as its collective emblem.

In this Street View, you can see the new Pegasus on top of the Magnolia Dallas Downtown hotel, looking up from Jackson Street:

Here's the original Pegasus, sitting on the Omni hotel lawn:

Bonus: Here's an Instagram photo of the original on the Omni Dallas lawn, and here's one of the new Pegasus atop the Magnolia.

Adolphus Hotel, Commerce and Akard

This December 1974 photo opens up another tale-of-twos from Dallas' past — the Adolphus and Baker hotels.

Credit City of Dallas Historic Preservation Adolphus Hotel, front, and Baker hotel, right, on Jackson Street, December 1974

The picture was taken from Jackson Street looking northwest toward Commerce Street. That's the Adolphus Hotel straight ahead.

Since opening in 1912, the Beaux-Arts style Adolphus has been one of the places to be and stay in Dallas:

In the Roaring '20s and into '30s, the hotel's Century Room nightclub hosted standing-room-only acts like the Andrews Sisters, Tony Bennett and Benny Goodman.

Local radio station KRLD 1080 AM began airing from the hotel in the 1930s, featuring stars like Bob Hope and Kate Smith for in-studio appearances.

From 1930 to 1965, the Century Room housed a retractable ice rink used for touring ice revues.

Guests have included presidents — Jimmy Carter, Ronald Reagan, George H.W. Bush — in addition to Queen Elizabeth II and Prince Charles.

The structure festooned with holiday garland on the right side of the image is what used to be the Baker Hotel, which was demolished in 1980.

The Street View below "stands" in the same spot as the person who took the 1974 photo. The Adolphus is still straight ahead but slightly obscured by tree coverage now. A newer Jackson Street sign stands in roughly the same spot, too. On the right, the spot where the Baker Hotel once stood is now the white-colored Whitacre Tower on the right — AT&T's corporate headquarters.

Speaking of the Baker Hotel ...

BONUS: Implosion of the Baker Hotel

Credit City of Dallas Historic Preservation The Baker Hotel

The city's Jennifer Anderson warns that this slide was not marked with an explicit description of what was happening or when. But the image appears to be of a crowd gathered to watch the implosion of the 54-year-old Baker Hotel, which took place on June 30, 1980. It looks like the camera shutter captured the bottom of the building just as it was beginning to crumble.

The Baker was the home of WFAA radio, and it was the place to stay (and party) on Texas-OU weekends, according to Dallas Public Library's Texas Archival Resources Online. Its Peacock Terrace Ballroom hosted big-name swing bands of the '20s and '30s. And long before the days of J.R. Ewing, the Petroleum Club met at the Baker.

Here's a 3D aerial image showing the AT&T headquarters — the building in the middle with the blue dot — where the Baker Hotel once stood.