1. Burj Khalifa is a skyscraper located in Dubai, United Arab Emirates. It is the tallest building in the world, standing at a height of 828 meters (2,716 feet). The building has 163 floors and was completed in 2009. It is primarily used as a mixed-use building, with office, residential, and hotel space. The observation decks on the 124th and 148th floors offer stunning views of the city, desert, and sea. The building also features a luxury hotel and several restaurants.

2. The working hours of the observation decks are from 8:30 am until 11:00 pm, and the last entry is at 10:00 pm. The contact number for Burj Khalifa is +971 4 888 8888.

3. The entry fee for the observation decks varies depending on the time of day and whether you choose to go to the 124th or 148th floor. It ranges from AED 149 (approximately USD 40) to AED 379 (approximately USD 103). Tickets can be purchased online or at the ticket counter on the lower ground level of the Dubai Mall. The nearest metro station is the Burj Khalifa/Dubai Mall station on the red line. Taxis and buses also provide transportation to the building.