A solarium is defined as a porch or room enclosed by glass, often intended for therapeutic purposes like relaxation and sunbathing. On cruise ships, the solarium is usually a glass-enclosed area with a pool, hot tub or thalassotherapy pool, plenty of lounge chairs and often a food service area.

Some cruise ship solariums have retractable roof panels that open for fresh air and sunshine when the weather is suitable. Windows along the sides of the ship may also open partially to create a fresh breeze through the solarium.

Often the solarium and its pools will be limited to use by adults only, or have hours designated for adults only, making it a quiet retreat for relaxation. On many ships, the solarium space is near, or has access to the spa, and food service in the solarium may be of a slightly healthier variety. It is often the place you will find fruit smoothies, whole grain breads, gluten-free offerings and healthy salads.