NEW YORK (CNNMoney) -- The wall along the Mexican border doesn't have to be made of boring concrete slabs.

It might be a "smart wall" filed with fiber optic cables designed to detect anyone trying to climb over or tunnel underneath it. Or it could resemble a medieval castle, with a notched top and turrets. It could be made of solar panels, or even be a work of art.

These are among the ideas submitted to the Department of Homeland Security, which is considering bids to build a barrier of some kind between Mexico and the United States.

This round of bids is actually to build a prototype for a wall, the first step in President Donald Trump's much repeated promise to build a border wall. Next, DHS will narrow down the list and request a handful of prototypes. The department declined to say how many proposals were submitted, but several candidates shared their plans with CNNMoney.

One of the more straightforward proposals comes from Quantum Logistics, which has built security walls for the U.S. military in Iraq and Afghanistan. Its pitch is to build a relatively simple wall with concrete slabs that are reinforced with steel bars. It would look something like the sound barriers along some U.S. highways.

DarkPulse Technologies wants to build a wall that has fiber optics embedded, in order detect attempts to tunnel underneath, climb over or breach the wall. DHS guidelines call for all wall submissions to go at least six feet underground to deter tunneling. But CEO Dennis O'Leary said that's just not enough, and points out that some existing border tunnels are as much as 80 feet underground.

"A six-foot foundation -- a couple of guys with a shovel can easily defeat that," he said.

The proposal from Crisis Resolution Security Services of Clarence, Illinois is inspired by the Great Wall of China and other ancient walls. It calls for a 30 foot dirt berm leading up to the wall's base, with a 26-foot wall on top of that. It will also have a four-foot safety rail along the top, so tourists can walk or even drive on the top of the wall.

"The wall will become a symbol of the defense of the American nation and culture, just as [the Roman Empire's] monumental wall defended the limits of the Western civilization," said the proposal.

Two proposals call for a wall that's covered on the southern side with solar panels, and has panels on the top that an be tilted during the day to capture the greatest amount of sunlight. Both suggest selling the electricity that the solar panels generate to offset the cost of the wall.

"Talking with young people, some of Spanish decent, they say if the wall is going to be built, they want it to be green," said Thomas Gleason, whose firm authored one of the bids.

Another solar wall proposal comes from a company called Advanced Warning Systems.

Some of the proposals submitted to DHS are more like political statements than practical suggestions for a barrier.

A group called Otra Nation, which is a collective of engineers, architects and designers, calls for the whole border area to be run jointly by both nations. Instead of erecting any kind of barrier, its plan calls for an elevated high-speed hyperloop that would stretch the length of the current border.

Another proposal is for a series of art installations involving tombstones, lighthouses and pipe organs playing music. The project was "submitted as a counterpoint" to the proposed wall, said Jennifer Meridian, its lead artist and designer.

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