HO UK model rail
My first permanent layout lasted for two years. It comprised of one long oval with a spiral incline, loop back crossover and siding.
A view of the foam baseboard supported by four Ikea trestle tables. The edges of the baseboard is taped down to the Ikea table tops with white Duck tape. A lightweight and firm base. It may not be constructed to last a thousand years, but it suits my purposes.