What makes Baku so challenging for the drivers?
First of all, it's a street circuit, which means that the cars race on relatively narrow roads - particularly in the old town - with tight walls and few run-off areas. While that doesn't necessarily make driving more difficult, it does mean mistakes have harsher consequences. If you get something wrong in Baku, chances are your weekend becomes much quieter while that of your mechanics is suddenly much busier.
What else makes it difficult?
Getting the tyres in the optimal temperature window is crucial; F1 tyres operate at temperatures around 100 degrees to provide optimal grip levels. However, making sure that the tyres, and, in particular, the front tyres, reach their performance window can be quite difficult in Baku. With the Azerbaijan Grand Prix taking place relatively early in the year, track temperatures are usually quite low; in fact, Baku has the potential of being the coolest track we will see all year.
During last year's race, track temperatures averaged about 25 degrees Celsius - a relatively cool surface for F1 tyres to drive on. And even on a sunny day, large portions of the track are in the shadow and don't warm up. The track layout adds to the challenge as the tyres cool down on the long straights and the slow corners don't create a lot of energy to warm them up. This challenge is exacerbated under Safety Car conditions when the cars have to go slower than usual, putting even less energy into the tyres. That's why aggressive tyre warming manoeuvres are quite common in Baku.