Alcoutim

Alcoutim sits on the Portuguese bank of the Guadiana about forty kilometres upstream from the sea, with the Spanish village of Sanlúcar de Guadiana directly opposite across a river a few hundred metres wide - two castles facing each other, built to watch one another. The Portuguese castle is fourteenth-century on earlier foundations, with an archaeological area inside showing Islamic-period remains, and a museum. Below it the village is white and very quiet, with a riverfront, a small marina and a ferry that crosses to Spain on request. Since 2013 a zip line has run from the Spanish side to the Portuguese one - the only cross-border zip line in the world, and because Spain and Portugal are in different time zones, riders land an hour earlier than they left. The upper Guadiana valley around is empty and hot - Alcoutim is the least densely populated municipality in Portugal.

What to look for

• The two castles - Portuguese and Spanish fortifications facing across the river.
• The zip line - a cross-border descent from Spain, landing an hour earlier by the clock.
• The riverfront - a quiet marina and a ferry crossing on request.
• The archaeology - Islamic-period remains excavated inside the castle walls.

When to go

March to June and September to November; summers on the Guadiana are extremely hot. Half a day. The zip line runs from the Spanish side and needs booking.

What to expect

The zip line starts in Spain, so riders cross by ferry first and it operates on Spanish hours. Very hot from June to September. The village is tiny with few services. The road from Vila Real is slow.

Nearby

Sanlúcar de Guadiana is across the river; Castro Marim and the salt pans are south.

Key facts