A more thorough explanation:

SOLARIUM

A solarium is a type of rent paid for a building that is built on public land. It is also known as ground rent.

1. In ancient Rome, people had to pay a solarium to the government if they wanted to build a house on public land.

2. The solarium for the commercial building was due at the end of each month.

The examples illustrate how solarium is a type of rent paid for a building on public land. In ancient Rome, people had to pay a solarium to the government if they wanted to build a house on public land. Similarly, in the second example, the solarium for the commercial building was due at the end of each month, indicating that it is a type of rent paid for the use of public land.