OLDEST - University botanical garden in the world — Padova, Italy - Superlatives on Waymarking.com

The Botanical Garden of Padua was founded in 1545 by the Venetian Republic, it is the world's oldest academic botanical garden that is still in its original location (older is the Orto botanico di Pisa, which was founded in 1544 however, that garden was relocated twice and has only occupied its current, and now-permanent, location since 1591).
The garden – affiliated with the University of Padua – currently covers roughly 22,000 square meters, and is known for its special collections and historical design. Six thousand types of plants are currently being cultivated and arranged according to taxonomic, utilitarian, ecological-environmental and historical standards. The systematic collection is concentrated in the four biggest central flowerbeds. Among the utilitarian collections, the medicinal plants are the most important.
The oldest plant is a palm planted in 1585 called the "Goethe palm", because the poet referred to it in his essay "Geschichte meines botanisches Studiums". This tree is situated in a greenhouse inside the Ortus Sphearicus. Other old trees are a ginkgo and a magnolia dating back to the mid-18th century, which are regarded as the oldest specimens in Europe.
In 1997, it was listed by UNESCO as a World Heritage Site because of the following reasons:
The Botanical Garden of Padua is the original of all botanical gardens throughout the world, and represents the birth of science, of scientific exchanges, and understanding of the relationship between nature and culture. It has made a profound contribution to the development of many modern scientific disciplines, notably botany, medicine, chemistry, ecology and pharmacy.

source: wikipedia, Università di Padova