Castles, palaces and monuments — hidden gems

In the free park of Karlberg Palace, in Stockholm, lie the grave of Charles XII's dog, the Temple of Diana and a runestone.

At 16 rue Chaptal, Ary Scheffer's hôtel with its courtyard and garden. George Sand mementoes, a free collection and a tea room in Pigalle.

In the City of London, a Victorian loggia with 54 tiles commemorates ordinary people who died to save others. A stone's throw from St Paul's.

In Berlin Mitte, the ruin of the Franciscan church from 1250: brick Gothic, free entry and art exhibitions, ignored by the crowds at Alexanderplatz.

Air-raid shelter 307 in Poble-sec, Barcelona: 200 metres of Civil War tunnels, visitable only on tours run by the MUHBA museum.

The oldest house in Athens is an Ottoman konaki in Plaka: a wine press, a courtyard with a well, and free admission at 96 Adrianou street.

On the Golden Horn, in Hasköy, an 18th-century Ottoman kiosk-palace with Venetian mirrors and a museum of Turkish musical instruments.

In Karaköy, a minute from the ferries, a wholly underground mosque in the dungeons of a Byzantine fortress. Squat pillars and three tombs.

Above Merano, Castel Tirolo guards a double chapel and Romanesque marble portals, reachable only on foot by leaving the car down in the valley.