Steel Plaza station

The Pittsburgh & Steubenville Extension Railroad Tunnel, also known as the Panhandle Tunnel, was originally built for the Pittsburgh and Steubenville Extension Railroad in Pittsburgh. It officially opened for rail traffic in 1865.

The James Reed Building or the Reed Smith Building is a historic building in Pittsburgh. It was constructed in 1902. It is in the Beaux-Arts architecture style. For many years, the primary tenant had been Reed Smith law firm. The buildings namesake is one of Reed Smiths founders, James Hay Reed. Reed Smith bought the nine-story building in 1984 for $5.82 million as 435 Sixth Ave Associates. In 2007 Reed Smith decided to relocate its corporate headquarters to Three PNC Plaza and sell the building, which had a market value of $16.78 million. The downtown Pittsburgh office vacancy rate at the time was 20%, driving down the value of the building. In October 2008, the building was purchased by Mika Realty Group of Los Angeles for $6.5 million. Mika Realty, owned by Michael Kamen and Gerson Fox, purchased the building under the name 600 William Penn Partners LLC. Kamen and Fox also purchased the nearby Union Trust Building 6 months prior.In 2009, Reed Smith law firm moved its corporate headquarters to Three PNC Plaza. Mika Realty was never able to find a tenant to replace Reed Smith, the building remained vacant, which led to bankruptcy in 2011. PMC Property Group purchased the building in September 2012 for $5.5 million in a U.S. Bankruptcy Court auction in Los Angeles.The building was redeveloped into a 249-room Hotel Monaco, opened in January 2015.

The Alcoa Building (a.k.a. the Regional Enterprise Tower) is a 410-foot-tall (120 m) skyscraper in Downtown Pittsburgh, Pennsylvania. It was completed in 1953 and has 31 floors. It is the 15th tallest building in the city and is adjacent to Mellon Square. A unique radiant heating and cooling system is contained in the ceiling: since there are no pipes, radiators, or air conditioning units along the exterior walls, an additional 15,000 square feet (1,400 m2) of rentable space was gained. Also, the windows rotate 360 degrees so they can be washed from the inside.Originally the headquarters for the Aluminum Company of America (ALCOA), the unique aluminum walls of the building are 1/8 inch thick, which gives the building a very light weight and economical design. It was the first skyscraper with an all-aluminum facade. Upon ALCOA's 2001 relocation to a new headquarters building on Pittsburgh's North Shore near PNC Park, the old ALCOA Building became a home to government entities, regional nonprofits and small start-up companies including the RIDC.

The Omni William Penn Hotel is a 23 floor (3 underground) hotel located at 530 William Penn Place on Mellon Square in downtown Pittsburgh, Pennsylvania. A variety of luminaries have stayed at the hotel, including John F. Kennedy. The hotel staff innovated Lawrence Welk's now famous bubble machine, and it was the site of Bob Hope's marriage proposal in 1934. The hotel has won numerous awards including being named to the "Best of Weddings 2009" list by The Knot and receiving the Editor's Choice Award in the Business Hotels category on Suite101.com. Omni William Penn Hotel, Pittsburgh is a member of Historic Hotels of America, the official program of the National Trust for Historic Preservation.The hotel also features an award-winning restaurant that dates from 1916, the Terrace Room, featuring among other amenities a wall long mural entitled "The taking of Fort Pitt". The Terrace Room was voted "Best Hotel Dining" establishment in both 2008 and 2009 by readers of the Pittsburgh City Paper.

The Allegheny HYP Club (Harvard-Yale-Princeton Club) is a private social club in downtown Pittsburgh, Pennsylvania. Located at 617-619 William Penn Place, it was built in 1894 and was added to the List of Pittsburgh History and Landmarks Foundation Historic Landmarks in 2002. On July 1, 1997, the club absorbed the Pittsburgh Club membership and assets.The Pittsburgh Harvard-Yale-Princeton Club was formally founded on November 7, 1930. The club merged with the Three Rivers Stadium based Allegheny Club in 2002 after Allegheny had filed for bankruptcy protection.

The Pittsburgh Central Downtown Historic District is a historic district in the Central Business District of Pittsburgh, Pennsylvania, United States. Bounded by Wood Street, Forbes Avenue, Grant Street, and Liberty Avenue, it was listed on the National Register of Historic Places on December 17, 1985. Its boundaries were expanded on May 2, 2013.The original district includes 26 buildings, 20 of which are considered contributing including a few small former residences built in the mid-19th century. The Frick Building and U.S. Post Office and Courthouse are contributing properties and are also listed separately on the National Register of Historic Places. Other notable contributing properties are the Gulf Tower, the William Penn Hotel, the Oliver Building, Mellon Square, the August Wilson Center, the Federal Reserve Bank Branch, Gulf Tower, the Frank & Seder Building, the Koppers Building and Trinity Cathedral.

Mellon Square is an urban park in Downtown Pittsburgh, Pennsylvania. It is the first Modernist park built above a parking garage. With its distinctive black, white and green geometric pavement, it is a prominent urban oasis and gathering spot in Downtown Pittsburgh. The square, bounded by Smithfield Street, William Penn Place, and Oliver and Sixth Avenues, is surrounded by prominent downtown buildings including the Oliver Building, 525 William Penn Place, Omni William Penn Hotel, and the Regional Enterprise Tower. It has long been a popular lunchtime destination for downtown workers. In addition, retail shops are housed underneath it, along the Smithfield Street side of the square.

The Bell Telephone Building is a 339-foot (103 m) art deco skyscraper in Downtown Pittsburgh, Pennsylvania. It was completed in 1923 and has 20 floors. It is the 22nd-tallest building in the city.

The Union Trust Building is a high-rise building located in the Downtown district of Pittsburgh, Pennsylvania, at 501 Grant Street. It was erected in 1915–16 by the industrialist Henry Clay Frick. The Flemish-Gothic structure's original purpose was to serve as a shopping arcade.

Koppers Building is a historical building in Pittsburgh, Pennsylvania, commissioned by Andrew W. Mellon and completed in 1929. The building is named after the Koppers Chemical Corporation and is one of the major features of Downtown Pittsburgh.

The Centre City Tower (also spelled Center City Tower) is a 341-foot (104 m) tall skyscraper in Pittsburgh, Pennsylvania. It contains 26 floors, and stands as the 20th-tallest building in the city. Centre City Tower was constructed in 1971, and was later renovated in 2002. The entire building contains Class B office space, and is an example of modern architecture. Signage for Huntington Bank, the building's major tenant, adorns the outside of the structure.

525 William Penn Place (also known as the Citizens Bank Tower) is a skyscraper located in downtown Pittsburgh, Pennsylvania. It was completed in 1951 for the Mellon National Bank and the U.S. Steel Corporation. At 520 feet (160 m) tall, it was the second-tallest building in Pittsburgh until 1970, and the third-tallest until 1984. The building has 41 floors and approximately 950,000 square feet (88,000 m2) of office space. Presently it is the third-largest office building by square feet in downtown Pittsburgh. In 2016, BNY Mellon sold the building for $67.65 million.