I spent time in Sarlat-la-Canéda, frequently called simply Sarlat, in the late spring of 2018 as part of a week-long stay in Périgord. Its charming medieval core is a maze of honey-colored buildings, narrow streets and passages, and hidden squares. Many of the major points of interest are clustered around wider spaces, such as Place de la Liberté or Place du Peyrou, but some are tucked away from the bustling central area.
The yellow Sarlat stone that is used in medieval buildings all over the department of Dordogne is the main architectural feature of the town, but there are also Renaissance stunners around, such as one of the visual symbols of Sarlat, Maison de la Boétie. They coexist with half-timbered belles, the legacy of Norman invasions of the 14th century. This mix of styles from different epochs makes Sarlat visually irresistible. Practically every building of note in the town center has a plaque or a stand in front of it with brief description of its history. You can give yourself a veritable guided tour of the town by focusing on those descriptions as you walk around.
Cathedral Saint-Sacerdos is relatively spartan in appearance, but not without a couple of standout features. The old church of Ste-Marie houses a small but delightful market. Manoir de Gisson offers a look into the living of local nobility.
I have certainly seen less atmospheric towns already bestowed with a WH designation. Sarlat is worthy of the inscription, whenever it may come, and would get solid 4 stars from me.