If you are travelling to a new city, you can use Google to quickly discover all the tourist attractions and other interesting places to visit in and around that city. This includes historical monuments, museums, gardens, and other places popular among tourists.
The syntax for your Google query should be Things to do in City. You may also use this query with a country - like Things to do in India - and Google will offer you a visual list of the top places to see in that country. It works for continents too.