The Grassmarket was one of fifteen different markets within the city of Edinburgh, formed under the 1477 ordinance of King James III [1460-1488]. For example, cotton and linens were sold in the Lawnmarket; corn in the Cowgate; cattle in King’s Stables Road and so on. The sale of live animals was forbidden in the town, and this was why cattle were to be sold outside the city wall at King’s Stables Road. This road was so named because the Royal horses were kept at the base of the Castle Rock.
This area of Edinburgh will be awash with Muggles so brilliant stealth will be required. Oh and don't forget your pen!.
Once you have found he cache make sure you check out the Grassmarkets fantastic shops, bars and restaurants.