On a budget, weigh it — Stonehenge (day-trip) isn't cheap for what it is.
£60–£100 (tour)
An ancient, genuinely mysterious monument that's smaller than people expect and roped off at a distance. The visitor centre adds context. Catch: it's ~2 hrs each way, often bundled with Bath/Windsor on a long coach day, and many leave underwhelmed if expectations are sky-high.