A working place of worship is public space with conditions attached

These are not museums that happen to hold services

The building exists for a congregation, and everything a visitor encounters follows from that. Opening hours are set around worship rather than around tourism, parts of the interior may be reserved, and the whole space can be closed at short notice for a funeral or a festival with no obligation to warn anybody who had planned to look at the roof.

A useful mental correction is to think of it as somebody else’s living room that happens to be open to the street. You are welcome, the welcome is genuine and often quite old, but you are a guest in a room that is being used for something, and the something takes precedence over the looking.

The distinction matters because a minority of these buildings have effectively become museums, with tickets, timed entry and a separate door for worshippers. Those are the exceptions, usually driven by visitor numbers large enough to make ordinary use impossible, and the conditions there are commercial as well as religious.

They are frequently the oldest and best-kept interior in town

Religious buildings survive because congregations maintain them across centuries, which is an unusual form of continuity, and because they were often the only structure a small community was willing to build in stone. In many towns the result is that the single most sophisticated piece of architecture available to look at is also free to enter.

What is inside is a layered record rather than a single design. Memorials, floor slabs, added chapels, replaced windows and repaired damage accumulate, and reading them gives you local history in a compressed and dated form: who the merchants were, which wars took people away, when the town had money and when it did not.

The furniture is informative too. Whether seating is fixed or movable, whether there is a pulpit or a platform, where the sound system has been installed and how the space handles the direction of prayer all tell you what actually happens in the room, which is more interesting than the style label.

They are used as shelter, meeting place and shortcut

In hot countries a shaded courtyard with water is a piece of public infrastructure, and it is used as one. In cold ones a warm interior open through the day serves the same purpose. Across a great deal of the world these buildings function as the room in which people wait, rest, meet somebody or sit down for twenty minutes without buying anything.

That role is under quiet pressure. Security concerns, theft and the cost of heating have led many buildings to reduce their open hours, and a church that used to stand open all day may now be locked except for services, with a keyholder named on a notice by the door. Asking at the address given usually works.

Many also run something practical: a food distribution, a language class, a night shelter, a concert series. If you are in a building at a time when one of these is happening, the appropriate response is to keep out of the way rather than to photograph it.

The conditions are mostly about dress, sound and photography

Covering shoulders and knees, removing shoes or covering the head are common requirements and they are almost always stated at the entrance in more than one language. Where a covering is needed, one is usually available to borrow, and using it without comment is the whole of the etiquette.

Silence is not always expected but restraint is. Conversation at ordinary volume is fine in many traditions and out of place in others, and the reliable signal is what the people already inside are doing. If everybody is speaking quietly, match them; if a service is under way, either join it properly or leave.

Photography rules vary and are worth actually reading rather than guessing. Flash is very widely prohibited because it damages pigments, tripods because they obstruct, and photographs of people at prayer because they are people at prayer. Where a donation is requested for photography, that is how the roof gets repaired.

Traditions differ, and the differences are not interchangeable

What is normal in one religion or one country can be wrong in another, including within the same faith, and the safest assumption is that the rules of the building in front of you are specific to it. Some interiors are open to all comers at all times; some restrict certain areas to members; some ask that visits avoid prayer times entirely.

There is also genuine disagreement inside these communities about how much visiting is welcome. Some congregations regard a stream of visitors as an opportunity and put out guides and leaflets; others find it wearing and would rather people came for the service or not at all. Both positions are reasonable and you will meet both.

None of this makes the buildings difficult to visit. It makes them a slightly different kind of place from a gallery, one where the correct posture is attentive and quiet, and where the reward for behaving like a guest is access to the most interesting interior for several streets in any direction.