The Diamond is the market square at the heart of Donegal town — a modest but pleasant open space surrounded by pubs, cafes, and shops, with a stone obelisk at the centre commemorating the Four Masters, the team of Franciscan scholars who compiled the Annals of the Four Masters in the 17th century. The obelisk was erected in 1937 and bears carved portraits of the four monks.
The square is the best place to start exploring the town: the castle is immediately visible from one corner, the main commercial streets radiate from the other sides, and the pubs around the edges are the centre of local life in the evenings. The Wednesday and Saturday markets bring food stalls and local produce sellers into the square. The atmosphere is entirely provincial Irish rather than tourist-oriented, which is exactly what Donegal town is.