Photo: Kim Traynor, CC BY-SA 3.0 via Wikimedia Commons
Over 150 years old, the Camera Obscura projects light from the top of the tower onto a large dish in a dark room below, displaying a panorama of the city. The effect still works on overcast days or at night but is best in sunlight, when you can use a sheet of paper to "pick up" people seen in the streets and have them scurry in your hand. The tower also houses a gallery of optical illusions that wouldn't be out of place in Blackpool.
Camera Obscura & World of Illusions is a tourist attraction located in Outlook Tower on the Castlehill section of the Royal Mile close to Edinburgh Castle. The original attraction was founded by entrepreneur Maria Theresa Short in 1835 and was exhibited on Calton Hill. Outlook Tower has been a museum since the late 1890s and is currently home to many interactive exhibits, including the original camera obscura.
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Thomas Gladstone was a wealthy merchant, and in 1617 he had this house refashioned to accommodate his family and to partly rent out. A "Land" means a tall narrow townhouse from the period when Old Town was cramped and the only space for development was upwards. Typically along the Royal Mile the ground floor was shops and trade, genteel folk lived on the first and second floors, and lower-income residents had to lump up many steps to the upper floors. It's now a museum run by the National Trust for Scotland exhibiting 17th century elite city life, richly furnished and decorated but with no running water. In the 18th century prosperous folk relocated to New Town, where the NTS property at 7 Charlotte Square continues the story.
Museum about money and coins, in the basement of the Palladian pile of the former Bank of Scotland headquarters. Scotland developed a banking sector in the 18th century to support long-distance trade, and still prints its own banknotes.
See Edinburgh#Connect for how to access. The internet stations are in the Learning Centre, and the building houses Central Lending Library, Central Reference Library, Central Children's Library, Edinburgh and Scottish Collections, Art & Design Library and Music Library. It has a wealth of material for research such as old newspapers and maps, but births, marriages and deaths are filed at East Register House by the bus station in New Town.
A venerable reference library, which you need membership to access, but it has public exhibitions about literature. "Treasures" is its permanent exhibition. But don't stumble in here mistaking it for Central Library across the street.
It's often called a Cathedral, but the Church of Scotland brooks no such episcopal entity, and Charles I dubbing it "cathedral" in 1633 was one reason his head was chopped off. Safer to call it "High Kirk", though they're nowadays lenient with first time offenders. The present building is from 14th century with much Victorian Gothic, notably its crowned spire. Highlight is the Chapel of the Order of the Thistle, Scotland's chivalric company of royal knights. Services are M-F at noon and 9:30AM and 11AM on Sunday, with choral music at 6PM.
Iconic fortress perched magnificently on a volcanic rock above the city. The castle has been continuously used for 1100 years and is kept in excellent condition; it's still the ceremonial headquarters of the army in Scotland. Highlights include the Great Hall, the Honours of Scotland (the Scottish Crown Jewels), the War Museum and the 12th century St Margaret's Chapel. The One O'Clock Gun is fired each day from Mills Mount battery. Audio guides available. It's mobbed with tourists and in summer often sells out, book online well in advance.