In the UK and Ireland stone circles are amongst the oldest built structures. They are usually mapped with historic=archaeological site, archaelogical_site=megalith. megalith_type=stone_circle. However, mapping in Wales it is soon apparent that there are quite a few modern ones.

Most are Gorsedd Stones, relics of National Eisteddfodau. However there’s a small covey near the entrance of the show cave at Dan yr Ogof. Most are mapped as monuments or memorials, although I think when the Eisteddfod returns to a site they are used for their original purpose.

Modern stone circles exist elsewhere, sometimes associated with the Welsh diaspora, as at the Plaza de Colonnes in Gaiman, Argentina (see image at top), and possibly in Hungary. Others, without a Welsh connection, include: replicas of Stonehenge (in a variety of materials) in the USA, Australia & New Zealand; and one in the grounds of the Glastonbury festival site.

Modern stone circles represent a type of tagging issue - the most widely used tag does not truly encompass all instances - which is not uncommon. Often these can be resolved by adopting a second more generic tag: one which is implicit from the first tag. A good example are disused telephone kiosks reused for other purposes. amenity=telephone describes a public pay payphone, but implicitly suggests a kiosk or booth (sometimes tagged as such using booth). Disused ones housing defibrillators, book exchanges etc. are often now tagged man_made=telephone_box **. Restaurants and bars in hotels are another example: often tagged bar=yes or restaurant=yes, particularly if these facilities are solely or predominantly for hotel guests. Minh Nguyen maintains a range of wikipages dealing with tagging issues of this kind related to synonyms, homonymy and antonyms. Although these are often easy to understand as a person because of context, they often create complications for interpretation by software, especially editors.

In this case I suggest man_made=stone_circle as a suitable encompassing tag for both ancient & modern ones. I’d also like to be able to map the stones. In some circles, henges and alignments the individual stones are themselves megaliths (also a historic tag), but there are many circles, whatever their age, where the stones are quite modest in size. ‘Stones’ may also be a misnomer as some Stonehenge replicas are made from a variety of other materials.

These mapping wants are a quirky little thing, but worth exploring. As here, modern versions of historical objects, whether replicas or re-imaginings (such as the development of commercial mausoleum in the form of long barrows) are probably the single largest category. However, there are others:

• Military vs sport shooting rifle ranges. Many of the latter may be mapped as leisure=pitch with sport=shooting, but this is not only misleading, but fails to provide for both indoor ranges and many outdoor ones such as those in Saas and Kublis. An added complication is that some sport shooting ranges are fairly closely integrated with military ones (ranges are so common in Switzerland because male citizens need to maintain & demonstrate continued proficiency).
• Estate agents, usually mapped with an office key, but there is a big difference between estate agents located on the high street in a retail property and one in a commercial district.
• Milestones has been accepted as the generic tag for all distance markers. However, there are both historic & modern examples. Obviously the original intent was to mark the former.
• Other historical examples : wayside crosses, tumuli and other burial mounds.
• Various types of marine rescue operations and facilities. Currently subject of a proposal vote.

There are three approaches:

• Use different keys, but often with the same tag value
• Subsume all objects under a single key-tag pair, perhaps using sub- or supplementary tags to distinguish types of objects. Thus modern instances of a typically historical object would still receive the historical key, but will be marked as different through another key.
• Treat the common base tag as a special case of another tag value which is implicit. This, in particular, is true of many things tagged with the historic key, where one might consider there is an implicit tag with the man_made key: in this instance man_made=stone_circle.

All of these will work for regular data consumers, but in the second case agreed subtags are important.

Ad hoc data consumers are less likely to be aware of their existence, or how they can change the base tag meaning, sometimes subtly, but in other cases drastically (as sport=shooting does on pitch). Probably, the choice of approach will depend on the nature of the tags, and the likely dissonance felt by map and app users: not sure that I’d be very chuffed it I went out of my way to visit a historic stone circle to find it was some blocks of concrete put in place a few years ago. Similarly if the remains of a loved one are interred at Soulton Long Barrow, I’m not sure I’d be pleased to see it marked on a map as an archaeological site.

** SomeoneElse points out that there are [many other ways)](https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L1782 of indicating a telephone box or kiosk.