A man rides on a a paternoster elevator in Prague, Czech Republic, Thursday, Sept. 7, 2017. For visitors to Prague, the recent opening of a rooftop terrace on the Art Nouveau Lucerna Palace building offers a double attraction: a sweeping rooftop view of the old town, and a rare ride in a paternoster _ a cyclic elevator with no doors that works on a circuit and never stops moving, a relic from a time when safety regulations were more lax, invented in the late 19th century, of which only about 200 to 300 are still in use in central and eastern Europe. (AP Photo/Adam Pemble)

PRAGUE, Czech Republic - For visitors to Prague, the recent opening of a rooftop terrace on the art nouveau Lucerna Palace building offers a double attraction: A sweeping rooftop view of the old town, and a rare ride in a paternoster — a cyclic elevator with no doors that works on a circuit and never stops moving.

Paternoster elevators were invented in the late 19th century, and some are still in use across Europe.

You can find dozens of them elsewhere in the Czech Republic, though they're mainly used by staff in government buildings. Not many are open to the public.

A few remain in Britain, where the paternoster had its origins, and Copenhagen has five. Danish lawmakers are often seen jumping in an out of them at the Christiansborg Palace, which houses the Danish Parliament.

There are as many as 200 still in use in the Germany.

The elevators feature two shafts side by side, with door-less cars slowly going up one side and then down the other in an endless circuit. You can hop on at one floor and off at another without ever pressing a button.

Paternoster is Latin for lord's prayer, and they got their name because each car runs on chains on a belt loop, a bit like the beads on a rosary.

Passengers are supposed to exit before the paternoster passes the top or bottom floor. If they don't, nothing serious happens, though they must wait to go around the top or bottom before heading back up or down in the opposite direction. Some make the turn just for fun.

The inventors of the paternoster saw it as a way to deliver more people up and down floors without a long wait, but they can be dangerous if they don't have an emergency off-switch.

At Prague's Lucerna Palace, which houses the Czech Republic's oldest cinema, a theatre, music venues and an ornate shopping gallery, tenants and workers use the paternoster every day. Now the public has a chance to ride too on days when the building's historic roof terrace is open. Organizers say they hope to do that for a week each month.

News from © The Associated Press, 2017