Yom Kippur is considered to be the holiest day in the Jewish calendar. People usually spend it fasting and praying. Therefore, on this day you can see how life in Israeli cities stops. All the shops, cafes and restaurants are closed, however, you can see people walking and socializing as no-one can work on the holiest day of the year. Another thing that may attract your attention - children on bikes. Kids are enjoying 24 hours when there are so few cars on the roads!
The biggest celebration hubs in the country are Tel Aviv and Jerusalem. One of the most well-liked activities in Tel Aviv on Yom Kippur is renting a bike and touring the city. Bikers will be able to effortlessly cruise throughout the city since congested streets like Ibn Gabriol and King George are car-free during the holiday. In addition, take a ride to Jaffa and Tel Aviv University. Always rent a bike in advance if you don't have your own.
If you're in Jerusalem for the holiday, be sure to visit the Western Wall or one of the major synagogues, such the Great Synagogue (the Kotel). It will be a lovely experience even if you are not accustomed to the prayer services. However, keep in mind that because synagogues are frequently crowded on holidays, you might need to stand near the back.