Corinth rewards a thin wallet: Acrocorinth, the largest castle in Greece, charges nothing, both canal bridges are free to walk, and souvlaki on the paralia costs under €3. Three days here run on about €25 a day, museum tickets included.
Greece's largest castle — 24 hectares of Byzantine, Frankish, Venetian and Ottoman walls on a 575m crag — charges no admission. Open roughly 08:00–15:30, with a car park just below the triple gate and a 40-minute climb to the summit.
The seven Doric columns of the Temple of Apollo (550 BCE) stand in full view from the free perimeter road and the village square, and the rock-cut Glauke Fountain sits outside the fence. The site ticket itself is €8 summer, €4 from 1 November.
The 6.3km cut is 79m deep and just 23m wide; from the old national-road bridge you look straight down sheer limestone walls onto ships under tow. Free to cross on foot at any hour, with free parking and a rest area at each end.
Paving from the 6th-century BCE stone trackway that hauled ships across the isthmus on rollers survives on the canal's west bank at Poseidonia. Unfenced, unstaffed and free, with late sun raking across the cut wheel grooves.
The open-air market runs Wednesday and Saturday mornings until about 14:00 on the streets off Adeimantou: Corinthian oranges, feta cut from the barrel, cured olives, Nemea grapes and greens at roughly half what tavernas charge.
The pedestrianised strip a block behind the waterfront is where Korinthos eats cheaply: pork or chicken souvlaki wrapped in pita with chips and tzatziki runs €2.80–3.50, while a plate of four sticks with bread and salad lands at €8–9.
The waterfront between the port mole and the clock tower is lined with kafeneia where a freddo espresso costs €2–2.50 and buys a table for two hours. Small boats land their catch at the mole, and Korinthos tap water is drinkable.
The town beach is a 15-minute shore walk west: a free pebble-and-sand strip with public showers, no sunbed charge beyond the two canteens, and sunset running straight down the Corinthian Gulf towards the Gerania mountains.
Host of the Isthmian Games, second in prestige only to Olympia. The stone starting gate of the stadium, the temple foundations and a museum holding the Kenchreai glass panels cost €4 together. Open 08:30–15:30, usually shut Tuesdays.
At the canal's eastern mouth the entire roadway sinks eight metres underwater to let vessels pass, then rises streaming with seawater. Free to watch from the bank, several times a day; the barriers dropping is your cue.
Corinth's western harbour silted into shallow lagoons, but the 5th-century basilica of Ayios Leonidas — at 180m long once among the largest churches in Greece — lies open on the shoreline, unfenced and free, with harbour channels still traceable.
A Frankish siege tower on the ridge west of Acrocorinth, reached by a rough 30-minute scramble off the Acrocorinth road. No gate, no ticket, no crowds — and the one viewpoint that holds the fortress, the isthmus and both gulfs in a single frame.