Viminacium is near the Serbian town of Kostolac, and river cruise ships sailing the eastern Danube stopover for a few hours so that passengers can tour the large Roman archaeological site. It's very interesting to look out over today's crop fields and imagine a bustling town and Roman fort from almost 2000 years ago.

The three areas at Viminacium open thus far include the northern Roman military gate, the thermal baths, and the imperial mausoleum. Guides, who may be either working archaeologists or professional guides, provide explanations, drawings, and models to help visitors understand what they are seeing on the tour.

Viminacium Imperial Mausoleum Graves (c) Linda Garrison

A great way to get a bird's-eye view of an old city is to walk on top of the ancient wall surrounding the town. Those who have cruised Europe can fondly remember walking the wall in Dubrovnik, Lucca, or one of the towns along the Danube River. And, of course there's that famous wall on the other side of the earth--the Great Wall of China. Yangtze River cruise tours always include a walk along this amazing structure.

The About.com Guide to Adventure Travel has compiled a list of her favorite "wall walks". Can you think of any others?

Dubrovnik (c) Linda Garrison

The Hluhluwe-Umfolozi (pronounced shu-shu-ee um-fo-loo-zee) Park is the oldest game reserve in South Africa. Established in 1895, Hluhluwe-Umfolozi is one South Africa park where the Big Five (lion, elephant, rhinoceros, cape buffalo, and leopard) can be found.

I visited Hluhluwe-Umfolozi Game Reserve in the early morning while on an African cruise on the Silversea Silver Wind. The ship stayed two days in Richards Bay so that passengers could do overnight excursions to other nearby game reserves like the St. Lucia Wetlands.

Zebra (c) Linda Garrison

The Parliament Palace in Bucharest, Romania is the second largest building in the world. Danube River Cruises in eastern Europe often include Bucharest as a port of call. A visit to this huge palace is a must see for Bucharest.

Bucharest Parliament Palace (c) Linda Garrison

More Photos of the Bucharest Parliament Palace