I'd better get my list in before I change it yet again:

No.1 /

Hal Saflieni Hypogeum

A wonderful subterranean complex which remained sealed and undiscovered for nigh on 4,500 years. Trilithons sculpted out of the rock; painted rooms.

http://www.themodernantiquarian.com/site/10617/hal_saflieni_hypogeum.html

No.2 /

Church Hole Cave at Creswell Crags.

No cave art was known in Britain until 2003 when a team of European archaeologists examined Church Hole Cave. I went as soon as I could and saw images of a deer, bird and bison from 13,000 years ago, in unfashionable Nottinghamshire.

http://www.themodernantiquarian.com/site/3067/creswell_crags.html

No.3 /

Stonehenge

It took me a few days to realise that I must nominate Stonehenge. The first ancient monument I saw, in the early '60s. Then there was a long gap until the mid 70's and the Summer Solstice festival years. Oh, happy days, which ended in tears and exclusion. The noughties brought us Open Access and, latterly, the Stonehenge Riverside Project, both of which I have enjoyed muchly.

http://www.themodernantiquarian.com/site/458/stonehenge.html