The grand heart of Santiago, the cathedral soars above the city centre in a splendid jumble of spires and sculpture. Built piecemeal over several centuries, its beauty is a mix of the original Romanesque structure (constructed between 1075 and 1211) and later Gothic and baroque flourishes. The tomb of Santiago beneath the main altar is a magnet for all who come to the cathedral. The artistic high point is the Pórtico de la Gloria inside the west entrance, featuring 200 masterly Romanesque sculptures.

Over the centuries the cathedral has suffered some wear and tear from water seepage, settlement and humidity, and a current restoration program means that you may well find much of the main (western) facade and the Pórtico de la Gloria covered in scaffolding. It's hoped that work on the Pórtico de la Gloria will finish by late 2017, but until then access to it will be restricted to a limited number of guided visits daily: check with the cathedral's Visitor Reception Centre for current information on these.

The cathedral we see today is actually the fourth church to stand on this spot. It has a traditional Latin-cross layout and three naves. The lavish baroque western facade facing Praza do Obradoiro was erected in the 18th century, replacing the weather-damaged Romanesque one. This is traditionally the cathedral's main entrance, but it's currently closed because of the restoration works. Most people therefore enter the cathedral through the south door on Praza das Praterías (beneath the only facade that conserves its original Romanesque structure). Inside, the fantastically elaborate, churrigueresque Altar Mayor (High Altar) rises up from the central crossing where the transepts intersect the nave, with the long main nave stretching away to the west, flanked by majestic rows of Romanesque arches.

From the right side of the ambulatory (walkway) that runs round behind the Altar Mayor, a small staircase leads up to a statue of Santiago that has watched over the cathedral since its consecration in 1211. The faithful queue up to kiss or embrace the statue. From here you emerge on the left side, then descend some steps into the Cripta Apostólica, where we are assured Santiago's remains lie, inside a large 19th-century silver casket. Behind the Altar Mayor is the Puerta Santa, which opens onto Praza da Quintana and is cracked open only in holy years (next in 2021).

A special pilgrims' Mass is usually celebrated at the High Altar at noon daily, with other High Altar Masses at 7.30pm and 9am or 10am. Touristic visits are discouraged during Mass.

For wonderful views of the cathedral's interior from its upper storeys, and of the city from the cathedral roof, take a cathedral rooftop tour.

The artistically unparalleled Pórtico de la Gloria (Galician: Porta da Gloria) stands just inside the cathedral's Obradoiro entrance, at the west end of the nave. If you're unable to see the Pórtico itself because of restoration works, you can at least visit an exhibition on it, which is being maintained for the duration of the restoration in the Pazo de Xelmírez adjoining the cathedral (access to the Pazo is included in tickets for the Museo da Catedral and the rooftop tour). The Pórtico features 200 Romanesque sculptures by Maestro Mateo, who was placed in charge of the cathedral-building program in the late 12th century. These detailed, inspired and remarkably lifelike sculptures add up to a comprehensive review of major figures from the Bible, with the Old Testament and its prophets on the north side, the New Testament and Apostles on the south, and glory and resurrection depicted in the central archway.

The main figure in the central archway is a throned, resurrected Christ, surrounded by the four Evangelists plus angels and symbols of Jesus' passion. In an arc above are the 24 musicians said in Revelations to sit around the heavenly throne. Below Christ's feet is Santiago, and below him Hercules (holding open the mouths of two lions). Visitors arriving in the cathedral traditionally said a brief prayer while placing their fingers in five holes above Hercules' head, created by the repetition of this very act by millions of faithful over the centuries. On the other side of the central pillar is a sculpture of Maestro Mateo. For centuries, tradition called for visitors to bump heads with the maestro to acquire some of his genius. These countless knocks led to Mateo's notably flat nose, and both he and Hercules were blocked off behind metal barriers even before the Pórtico acquired its recent scaffold covering.

Among the Old Testament prophets, the very bright smile on Daniel's face is, according to one legend, caused by the tightly dressed figure of Queen Esther on the pillar opposite him. Legend also has it that Esther's stone breasts were originally much larger, but were filed down on orders of a disapproving bishop – to which townspeople responded by inventing Galicia's cone-shaped tetilla (nipple) cheese in Esther's honour.