All ages
Destination: Sultanahmet, Istanbul, Turkey

Istanbul is a city with a foot in both Europe and Asia, and its religious heritage is equal parts Islam and Christianity (even its Christian history is half Roman Catholic, half Greek Orthodox). The kids may not always be able to keep all these elements straight, but they'll at least remember the exquisite mosaics and domes.

The masterpiece is Ayasofya, which for almost a thousand years was the largest Christian church in the world (the Statue of Liberty's torch would barely graze the top). Built by the Emperor Justinian in A.D. 537, it became the symbol of Byzantine power. Its history has been turbulent; for one thing, in this earthquake- prone region, clunky flying buttresses had to be added to support its red-tinted outer walls. In 1204, the Crusaders stripped the church of its relics, a sacrilege that caused the Greek Orthodox Church to split from the Roman Catholic Church. Then, in 1453, Mehmet II took over the city (look for his stone cannonballs along the path in the inner courtyard), and his first official act was to declare the great church a mosque. Frescoes and mosaics were covered up, as Islam forbids the representation of figures; slim pointed minarets were erected; the altar was shifted to accommodate a mihrab (a niche pointing toward Mecca); and an ablution fountain was plunked down in the courtyard. In 1935, when Atatürk converted it to a museum, its hidden mosaics and icons were restored.

The Byzantine church will astound you, with some 1.6 hectares (4 acres) of mosaics covering the interior. The glistening narthex, or inner vestibule, is just the prelude; the 15-story-high main dome is crowned with 40 windows to filter light onto its gold mosaics. Point out to the kids that, per Islamic tradition, many mosaics have calligraphy or abstract motifs; go up in the southern gallery to find the really old ones with pictures.

When Sultan Ahmet I built his namesake mosque in 1609, the beauty of Ayasofya so galled him, he set out to surpass it. The result is the Blue Mosque, a grand bubble of masonry that's a defining feature of Istanbul's skyline, with its cluster of domes and minidomes and its six gold minarets (the mosque in Mecca had to add a seventh minaret to top it). You enter through a door off the Hippodrome (remove your shoes!), beneath a symbolic chain that required even the sultan to bow his head when he arrived on horseback. The kids will be awed by the girth of the "elephant foot" pillars supporting the series of domes overhead. As the sun pours in through 260 windows, the lofty space swirls with colors from the exquisite decorative tiles -- mostly blues and greens, of course, hence the name.

Information: Ayasofya Museum (tel. 90/212/522- 1750).

Nearest Airport: Atatürk International, Istanbul.

Accommodations: Çiragân Palace Hotel Kempinski Istanbul, Çiragân Caddesi 32 (tel. 800/426-3135 in the U.S., 90/212/326-46-46 in Istanbul; Blue House Hotel, Dalbasti Sokak 14 (tel. 90/212/638-9010;