... in an open door
When I was younger my father used to take us on country walks and we'd pop into the churches in the villages we went to. If the door was locked, he was always very disappointed. I know there are lots of reasons why churches are locked, but in principle its a very fine thing if they can be kept open.
Particularly churches in the cities. For example I ate my lunch in Mount Street Gardens, and many people who work in surrounding Mayfair come to eat their lunch too. Some of them are content to be surrounded by the beautiful flowers, but sometimes people come up to the church and want to have a look around. Some of them are tourists who may have read about the church in a guide book. The same is also true of many other churches, including Westminster Cathedral which is open from 7 until 7 on most days. The interaction people are able to have with churches that are open in the middle of the day is wonderful.
I have a friend who has stated previously that he doesn't like to go into churches because he doesn't feel comfortable in them as an atheist. That's fine. But he makes an exception for the Catholic cathedral in Liverpool, which he thinks is amazing. (Whenever people criticise modern church architecture, I think of this). Churches are not always good at allowing or encouraging this kind of spiritual tourism, yet I think it is very important. If the door is open, someone may walk through it. If there's a welcome, then who knows what wonders God can work in that person.