Luxembourg Hauptbahnhof

Yes. Public transport is free nationwide, which removes the ticket and platform-pass question that's otherwise present everywhere for spotters. You reach every platform in the country without any formality. For cross-border journeys to Germany, France or Belgium you do need a ticket, though – only the section within Luxembourg is free.

Three: Germany via the Moselle axis towards Trier, France via Lorraine towards Metz and Thionville, and Belgium via the Ardennes line towards Arlon and Brussels. Add to that long-distance traffic from Paris. No other main station offers this combination at this density – the closest comparison is Basel SBB, with three railway administrations involved.

Because the electrification systems in the approach differ. Any vehicle that's going to cross the border has to handle several systems – add to that different train protection systems on both sides. For spotters that's the real reason to come here: such vehicles stand side by side as a matter of routine, not as special cases. How border stations work operationally is explained in the article on border stations.

In regional and commuter traffic, double-deck multiple units dominate, above all the CFL Class 2300. On long-distance services towards Paris the TGV is used, and in freight traffic modern multi-system locomotives such as TRAXX and Vectron. The country's own fleet is small and largely covered in a single day.

At the main station, mostly as a transit. The real hub is Bettembourg south of the city, with a terminal for combined transport and connections far to the south. The platform there is publicly accessible, and the journey only takes a few minutes. Anyone who wants background reading beforehand will find the basics in the guide to marshalling yards and the article on freight wagon types.

On weekdays during rush hour, so morning and early evening. Luxembourg lives on cross-border commuter traffic, and in these windows trains from all three directions arrive at the same time. Outside these peaks and during school holidays the frequency drops noticeably – that's when a side trip to Bettembourg is worthwhile instead.

Moderate on the platforms, because they're covered. The platform ends jut out partly and are therefore the better viewpoints: south end in the morning, north end in the afternoon. Reckon with ISO 1600 or more under the roof. How to work out the light beforehand is covered in the article planning the sun's position at a photo spot.

Very much so. There's no ticket question, the station is clearly laid out, the walks are short, and it's noticeably quieter than at the big neighbouring hubs. At the same time you see more different vehicles here than at many larger stations. How to turn that into a structured session is covered in the guide planning a spotting tour at a station.

On the publicly accessible platforms and around the station, photography for private purposes is common. As everywhere, the operator's house rules apply, and track areas, shunting and operational land are off limits without exception. In practice the attitude here is more relaxed than at French main-line stations – which isn't a blank cheque. The general principle is described in the article on house rules at a station.

The main station alone isn't – the fleet is too small for that. Combined, yes: morning at the main station, midday at Bettembourg, afternoon a cross-border trip towards France or towards Belgium. Because local transport in the country is free, these moves cost you nothing but time.