I notice that there are a few WHS which have been assigned to a Time Line period but whose "descriptions" lack a date to justify/explain.
It would seem worthwhile to try to provide more specific info where possible! I make a start below starting from the 20th C and working back. I have tried always to find at least 1 specific year date to justify the assignment.20th CBahai Holy Places
- Precise location for tomb determined in 1891... "The remains of the Báb were buried on March 21, 1909 in a six-room mausoleum made of local stone. In a separate room, the remains of `Abdu'l-Bahá were buried in November 1921. In 1929 three rooms were added to the mausoleum, and in 1949 the first threshold stone of the superstructure was laid by Shoghi Effendi. The construction was completed over the mausoleum in 1953" (Wiki)19th CVienna
- The Ring "was constructed after the dismantling of the city walls in the mid-19th century. From the 1860s to 1890s, many large public buildings were erected along the Ring Road in an eclectic historicist style, sometimes called Ringstraßenstil ("Ring Road style")," (Wiki)First Coffee Plantations
- "Coffee production was established in the island of Saint-Domingue (Hispaniola) by French settlers in the 18th century. The uprisings from 1790 onwards, culminating in the establishment of the independent state of Haiti in 1804, resulted in the flight of French plantation owners, accompanied by many of their African slaves, to the neighbouring island of Cuba, then under Spanish rule. They were granted lands in the south-eastern part of the island in the foothills of the Sierra Maestra, at that time largely not settled and eminently suitable for coffee growing" (AB)18thCVienna
- Baroque e.g Lower Belvedere from 1712, Upper Belvedere 1717-1723. See https://en.wikipedia.org/wiki/Category:Baroque_architecture_in_ViennaLednice-Valtice
- Straddled 17th-19th Centuries. "The realization of this grandiose design began in the 17th centurv with the creation of avenues connecting Valtice with other parts of the estate. lt continued throughout the 18th centurv with the evolution of a framework of avenues and paths providing vistas and rides, imposing order on nature in the manner of the Renaissance artists and architects. The early years of the 19th century saw the application by Duke Jan Josef 1 of the English concept of the designed park" (AB)City of Bath
For its Georgian buildings and heyday as a fashionable spa town - "The Assembly Rooms, built in 1771 by John Wood, Jr. and the Pump Room from 1793 to 1799 by Palmer in accordance with the plans Thomas Baldwin) harmonize with the grandiose proportions Assembly built of of monumental ensembles such as Queen Square (1729) and the -Royal Circus (1754), both works of John Wood Sr.; and especially, the Royal Crescent, an extensive row of dwellings in a half-circle formation built from 1767 to 1776 by John Wood" (AB)Summer Palace
"During the reigns of the Qing Emperors Kangxi and Qianlong (1663-1795) several imperial gardens were created around Beijing, the last of them being the Summer Palace, based on the Hill of Longevity and Kunming Lake in the north-western suburbs of the city.... Between 1750 and 1764 Emperor Qianlong created the Garden of Clear Ripples, extending the area of the lake" (AB)Diamantina
- "The town of Diamantina .... developed in the 18th century.......the discovery in 1720 of an unsuspected source of wealth, diamonds.....(When) the Portuguese Crown discovered the existence of this source of wealth in 1731, it set up a new body to administer the region, the Demarcação Diamantina.... Two sets of 18th century plans show a layout of winding and uneven streets which have changed little since that time." (AB)
Enough for now!!!