The Tron Kirk is a former principal parish church on the Royal Mile in Edinburgh, now best known as a historic building repurposed for markets, exhibitions, and events.
The Tron Kirk (often called “the Tron”) was built between 1636 and 1647 as a reaction‑plus church for Edinburgh’s South‑East (later North‑West) parish, commissioned by King Charles I when St Giles’ was made a cathedral.  It closed as an active church in 1952 and has since been used as a tourist information centre, exhibition space, and more recently as a boutique arts and crafts market.
The “Tron” in the name comes from the public weighing beam (Scots: tron) that once stood by the market on the Royal Mile, north of the kirk.  The building still sits on the High Street section of the Royal Mile
 
Interesting facts...
 
The church sits on a lost street. The kirk is built over the buried remains of Marlin’s Wynd, a 15th–16th‑century close whose tenements were demolished to make way for the church.Archaeologists in the 1970s found paved sections of the wynd and old vaulted cellars beneath the floor; this stretch is now thought to be the oldest surviving paved street in Scotland.