At North Korea’s new beach resort, the white sand glistened against the crystal-clear waters. Ten minutes of Wi-Fi cost $1.70. Food arrived in abundance, albeit with the same three beverage choices: water, tea or beer. The weeklong trip cost roughly $2,000. The catch? All travelers had to be Russian. Welcome to North Korea’s Wonsan Kalma coastal complex, a megaresort built by the regime to portray the country as modern and affluent. It is opening to foreign vacationers for the first time, as part of North Korean leader Kim Jong Un’s drive to attract more tourism to his cash-strapped country and...