The Isle of Man TT (Tourist Trophy) motorcycle races are held every year during the last week of May and the first week of June. It's one of the oldest - and also one of the most demanding and dangerous - motorcycle meets on the calendar. Wikipedia notes:
The future of the TT is always in doubt with regards to ... safety, especially "Mad Sunday" when any member of the public can ride the mountain section of the course which is open one way from Ramsey to Douglas. The TT races are extremely dangerous because of the high speeds on very narrow, twisting streets, roads and lanes flanked by stone walls and even buildings. Between 1907 and 2009 (at the end of [the] 2009 TT races period) there have been 237 deaths during official practices or races on the Snaefell Mountain Course.
There's more at the link. Bold print is my emphasis.
The TT demands astonishing levels of skill from participants. Average speeds of over 120 mph are common on the almost-38-mile course, with top speeds approaching 200 mph recorded at some points. Here are two video clips to show you just how demanding (and dangerous) the course is. I highly recommend watching both in full-screen mode.
The first is a short aerial view of Guy Martin on his Suzuki GSX-R1000 superbike. Note how his speed is so great that he outpaces the camera helicopter on more than one occasion! The aircraft can only keep up with him by 'cutting corners' between bends.
Next, here's an eighteen-minute driver's-viewpoint look at the entire circuit. Note how fast the road signs, spectators and landmarks flash by!
I enjoyed many years riding larger bikes of the touring variety, culminating in a BMW R100RT . . . but you wouldn't get me aboard one of those high-performance two-wheeled demons if you gave me all the gold in Fort Knox! I know my limitations!