Downtown Dubai's two headline attractions on one ticket, and they sit a few minutes' walk apart, which is what makes the pairing work. At the Burj Khalifa, the world's tallest building, a high-speed lift reaches the At The Top observation decks on levels 124 and 125 in about a minute, opening onto an outdoor terrace with telescopes and an uninterrupted view over Downtown, the coast and the desert beyond. On the ground floor of Dubai Mall, the Dubai Aquarium holds ten million litres of water and more than 140 species, including around 300 sharks and rays and one of the largest sand tiger shark collections anywhere; the ticket covers the 48-metre walkthrough tunnel and the Underwater Zoo above it, home to penguins, otters and King Croc. Allow around an hour for each. Both are indoors and air-conditioned, and evening slots at the tower are worth booking ahead - they sell out first.