Without a doubt Jvari, meaning cross in English, is the most frequently visited place for tourists on a day trip from Tbilisi and it is nearly always crowded nowadays. The church, a UNESCO World Heritage Site, is perched on a hill and is clearly visible when heading out of Tbilisi on the Georgian Military Highway.
The church dates back to the 6th century and offers jaw-dropping views over the Mtkvari and Aragvi rivers. Even Mount Kazbegi, some 150 km away, is visible in the distance on a clear day. Beware of windy weather in the winter months!
Getting there: a taxi from Mtskheta can be negotiated for between EUR 7-10 for a roundtrip. The best option would be to combine other nearby areas such as Svetitskhoveli, Samtavro and Shio Mghvime (EUR 25-30 roundtrip) following this link. Another option is to visit Jvari from Tbilisi, in combination with a stop in Mtskheta and exploring the surrounding area.
