Paris has an extensive public transportation system that includes buses, trains, and subways. Travelers can purchase a 1-5 day pass that covers unlimited rides on all modes of transport. A single ride on the subway costs around $2, and a taxi from the airport to the city center costs around $50.
If you have more time, you can explore other famous landmarks such as the Palace of Versailles or the Arc de Triomphe. However, if you have less time, consider skipping some of the museums and focusing on outdoor attractions. It's also recommended to avoid visiting Paris in peak season (July-August) to avoid large crowds and high prices.