Hikers in Iceland can enter the massive, empty magma chamber of the dormant volcano Thrihnukagigur, which rises 100 feet above Bláfjöll County Park and last erupted 4,000 years ago. 

From May 15 to Sept. 30, five tours a day are led by 3H Travel (phone +354 863 6640). On a 50-minute “moderately difficult” hike, the group walks two miles across hilly and uneven but mostly level lava fields; the last 10 minutes to the top of the volcano are the most challenging.

Small groups then...

In Abu Dhabi, the package “Desert Safari Half Day,” 2-8 p.m., visits the Rub' al-Khali, the world’s largest sand desert, and includes pickup and drop-off, Arabic coffee and dates, sand boarding, ATV dune bashing, horse and camel riding, a goat farm visit, a falcon show, henna tattoos, a barbecue dinner and a viewing of the desert sunset. $68 adult, $48 child (age 4-12). 

More intrepid travelers can stay overnight in a traditional tent and bed. $95 adult, $80 child. There also is the...

2014 marks the 100th anniversary of the start of World War One. The war officially began on July 28, 1914, when the Austro-Hungarian Empire declared war on Serbia. Through 2018, nations throughout Europe are holding events, including battlefield tributes in Belgium and France, reenactments, remembrances at war cemeteries and museum exhibits. 

On Oct. 3, 2014, Belgian and Dutch armies will build a pontoon bridge across the River Scheldt, one of the last barriers the Allies had to cross...