Kew Gardens, London
The area started as royal estates and gardens in the 1200s. Throughout the reigns of various kings and queens, land was acquired, more gardens built, buildings rose and fell, and in the 1700s the estates were merged into a large botanical garden. In the 1840s, it was formally declared the royal botanical gardens (which today means while it 'belongs' to the monarch, it's really a treasure of the state).The gardens are used not only to collect, but to test and verify transplanted species from around the world (to break the monopoly those places had on these plants, like rubber and spices). This proved a very important economic factor as wars for over 100 years were fought over unique plant environments by the English, which is quite costly.
In the past, it fell into disrepair but the last few decades have seen a very concerted effort of conservation and upkeep that has it at an amazing state.
The Arrival - Kew Gardens Station
I took the District Line (you can also take the Overground train line) to Kew Gardens Station, which is a good hike from the gardens, but the closest you can get.There is a little market area around the station which has a very comforting Victorian style.
Once you get there, the line to get in is crazy, but you can prepurchase your tickets online.
The Grounds
Being geared toward plants, you'll spend most of your time outside and it's a massive amount of land to cover. There are open air trams to drive you around, but I walk to try to lose some of this traveler's fat I get from drinks and sitting on planes all the time.Inside buildings
There are plants that even gulf stream fed England cannot support outside, and they have particular buildings to provide the environment required by the plants in them. The Lily house is one I did not go in, but the Palm House and the Temperate House were both pretty nice to wander though.Summary
Kew Gardens boasts the largest collection of plants in the world, the oldest wrought iron glass house and the largest glass house in the world, a large array of places to eat, have tea, and relax. Visiting is an entire day affair.And of course there's a gift shop with tons of horticultural items and some other things that have me scratching my head.