A Spanish company director flies to Vienna to attend a business conference where he is to give a promotional presentation about his company. He is staying at a hotel owned by a company headquartered in Madrid. One morning, while walking downstairs to have breakfast in the hotel restaurant, he slips on some water at the top of the stairs, falls and breaks his leg. He spends two weeks in hospital and is unable to attend the conference. He wants compensation for his medical expenses, hotel and travel costs, and lost business opportunities.

Which law applies to this case?