I honestly thought this was a WHS (the spanish wikipedia says so...)
David Gareji monasteries IS a set of monastic complexes, atop a desertic plateau in the border between Georgia and Azerbaijan. The landscape itself IS nothing short of spectacular.
This place is HUGE. It was a very important pilgrimage site from the 11th to the 13th century, home to a thriving school of fresco painters funded extensively by the georgian kings.
Most people visit David Gareji in the georgian side and udebno in the azeri side. Getting there requires some determination but thankfully no border control. To put It bluntly, the site is in the middle of nowhere and the roads are quite bad.
David Gareji itself doesn't boast much as far as I remember, but It's probably the first complex you'll see. The true highlight of the visit IS imo udebno, which is accesible via David Gareji. The path IS a bit hard to find. My recomendation? you can find detailed instructions online: FOLLOW THEM and if you're lost ask the border guards. What awaits you IS a cornise filled to the brim with caves decorated with religious paintings from the 8th century onwards. Dozens of them, scattered across the cliff. The caves themselves are not protected (thus Many are vandalized) and some of them are...dubiously accesible, so visiting them feels a bit like an adventure. As you finish the path across the precipice, which Will take you a couple hours you can see other caves in the distance, not accesible yet, but surely equaly impressive.
Out of all the sites we saw in Georgia and armenia we chose unanimously David Gareji as the most impressive.