Stonehenge Prehistoric Monument
The best time to visit Stonehenge is either early in the morning (as soon as the site opens) or late in the evening (two hours before they close). In the morning you'll avoid the most crowds that way, as the tour buses usually start to arrive around 10 am. In the summer you can capture stunning sunset photos when arriving in the evening.
Booking in advance is highly recommended: Stonehenge Admission Ticket. To avoid the busier times book either the first slot (9:00 AM in summer / 9:30 in winter) or the very last slot (different times depending on the season). Additionally, try to avoid weekends.
Best light for photos is in the morning. Another way to avoid crowds is booking a private sunset tour, where you could even take stunning golden hour shots. We highlty recommend this one (it's excellent): Stonehenge Private Sunset Tour from London - With Lacock and Bath
With an age of 4000 to 5000 years, it has an immense cultural value. Many visitors are present year round. The site is located directly at the A303, thus it is very easy to reach. There is a path around the complete monument, and you are not allowed to get in direct touch with the stones. Therefore you will always have a good view of the monument and may get good pictures.