If you're looking for some great day trips from Tbilisi that you can take by car, here are some suggestions:

Mtskheta. This ancient city is only about 20 kilometers from Tbilisi and is home to several historic sites, including the Jvari Monastery and Svetitskhoveli Cathedral. You can easily spend a full day exploring the city and its surroundings, taking in the stunning views and learning about Georgia's rich history.

Gori and Uplistsikhe. Gori is the birthplace of Joseph Stalin, and you can visit his childhood home and museum there. Uplistsikhe is an ancient cave city that's carved into the side of a cliff, and it's just a short drive from Gori. You can easily visit both places in a day trip from Tbilisi.

Signagi and the Wine Region. Signagi is a charming hilltop town in the heart of Georgia's wine region. It's about 120 kilometers from Tbilisi, but the scenic drive is definitely worth it. Once you're there, you can explore the town's cobblestone streets, taste some delicious Georgian wine, and take in the stunning views of the surrounding vineyards.

Borjomi National Park. This beautiful national park is just a few hours' drive from Tbilisi, and it's a great place to spend a day hiking and enjoying the natural scenery. You can also visit the town of Borjomi, famous for its mineral water and scenic park.

Kazbegi and the Georgian Military Highway. This scenic drive takes you through the heart of the Caucasus Mountains, and offers stunning views of Mount Kazbek and the surrounding landscapes. You can visit the picturesque Gergeti Trinity Church and explore the town of Kazbegi before heading back to Tbilisi.

These are just a few of the many day trips you can take from Tbilisi by car. Just be sure to plan your route in advance and leave early in the day to make the most of your time. Also, keep in mind that some of the roads can be winding and hilly, so be prepared for some slower driving at times. Enjoy your adventures!