It's a Monorail system inaugurated in 19-freaking-oh-one, with Kaiser Bill as a passenger on a test run from 1900. Still in use today, with 72,000 daily passengers.
It makes a cameo in Episode 7 of Connections, "The Long Chain" (and in the Princess and the Warrior). The episode is one of my favorites. It takes us from the fluyt through the British need for pitch, to a coal tar substitute, which yields many delightful things, including gaslight, the Mackintosh, and an attempt at synthetic quinine that results in the first aniline dye, mauveine, ushering in the Mauve Decade.
On to acetylene, the Wuppertaler monorail, WWI and the blockade of Chile (source of nitrates - also site of Britain's first loss in a naval battle in a century (though soon rectified)), pushing the development of artificial fertilizer and explosives, and thence to the 1939 World's Fair, nylon, and I just want to say one word to you. Just one word. Plastics.