1. Puerta del Sol is one of the most famous and busiest tourist attractions in Madrid, the capital city of Spain. It is a public square that is located at the heart of the city, and serves as a central hub for transportation, shopping, dining, and entertainment. The name \"Puerta del Sol\" means \"Gate of the Sun\" in Spanish, and the square was originally named after the eastern gate (\"Puerta\") that led to the city’s central area.

One of the most interesting facts about Puerta del Sol is that it is considered to be the \"kilometer zero\" (Km 0) of the country. This means that it is the starting point of the national highway network, and all distances in Spain are measured from this point. Puerta del Sol is also surrounded by several historic buildings and landmarks, such as the clock tower, the statue of King Carlos III, and the Royal Post Office.

2. The Puerta del Sol is open 24 hours a day, 7 days a week. There is no admission fee. Phone number is not available for Puerta del Sol as it is a public square.

3. Puerta del Sol has excellent public transportation links, including metro, bus, and taxi. The nearest metro stations are Sol (Lines 1, 2, and 3) and Opera (Line 5). The bus lines that serve the square include: 3, 5, 46, 51, 52, 53, 150, and 202. It is recommended to use public transportation as parking facilities are very limited in the area.