solarium

Concise Oxford English Dictionary © 2008 Oxford University Press:
solarium /səˈlɛːrɪəm/

▶noun (pl. solariums or solaria /-rɪə/)

• 1 a room equipped with sunlamps or sunbeds.

• 2 a room fitted with extensive areas of glass to admit sunlight.

– origin C19: from L., lit. ‘sundial, place for sunning oneself’, from L. sol ‘sun’.