In 1861 Twain headed west with his brother Orion who had been appointed Secretary to the Northern Territory. He settled briefly in Carson Cit, Nevada, before relocating to San Francisco where he became a regular newspaper correspondent and a contributor to the literary magazine Golden Era .

Twain's first trip "abroad" was to the Sandwich Islands, now Hawaii, in 1866 and the following year he travelled to Europe to report on the first-ever organized cruise to the Azores, Morocco, Spain, Gibraltar, France, Italy, Greece, Turkey, and the Holy Land. The Innocents Abroad (1869), an often irreverent satire of Mediterranean culture and its antiquities, put Twain's name on the map as America's first travel writer.

Unfortunately, Twain's success was plagued by frequent bouts of writer's block. He tried desperately to overcome them by starting several books at one time, but when Tom Sawyer (1876) wasn't the success Twain had counted on, he developed a particularly severe blockage. Nothing helped; not his beloved wife Olivia Langdon; not her considerable wealth; not even their adorable daughters Clara and Susy.

In extremis, in March 1878, Twain decided to embark on a second trip to Europe. His goal was to write a second travelogue and to finish his several pending novels, among them The Adventures of Huckleberry Finn and The Prince and the Pauper . In the opening paragraph of his amusingly self-illustrated A Tramp Abroad , he explains:

"One day it occurred to me that it had been many years since the world had been afforded the spectacle of a man adventurous enough to undertake a journey through Europe on foot. After much thought, I decided that I was a person fitted to furnish to mankind this spectacle. So I determined to do it."

After all, The Innocents Abroad a decade later was still America's most popular travel book. Twain hoped that his intended "tramp" or walk across Germany, Switzerland, and northern Italy — places he'd never seen — would be its sequel.

In a note "To The Reader" he explains his choice of title:

"Perhaps you were about to say that formerly I went Abroad as an Innocent, but that this time, fortified with experience and guile, I went Abroad as a Tramp...When I chose my book's title, I only intended to describe the nature of my journey, which was a walk , through foreign lands, — that is a tramp...I had a couple of light minor purposes, also: to acquire the German language and to perfect myself in Art."

Supposedly looking for a quiet village, where people didn't know him, neither of which fit Heidelberg because it was already home to active American and British communities, he arrived with his family on May 6 for the day and stayed three months. His biographer Justin Kaplan asserts Twain was aware that Heidelberg derived from "Heidelbeerenberg", meaning "Huckleberry Mountain", which may explain his affinity.

"Nobody really knows," writes Werner Pieper in his updated Mark Twain's Guide to Heidelberg , "what made Mark Twain stay in Heidelberg for such a long time. Maybe he was prompted by old dreams from the times he was passing Heidelberg, Mississippi, while working on the steamships? Did he plan to stay here or did he and his family just fall in love with this city?"

If so, Mark Twain wouldn't be the only one. Today more than 2.5 million visitors crowd its narrow, twisting streets every year. I recently followed "In the Footsteps of Mark Twain", a tour set up by Heidelberg's Convention and Visitors Bureau last year to celebrate the 125th anniversary of his sojourn here.

Like Twain, I stayed at the Hotel Schrieder, today the super-comfortable Crowne Plaza, where the breakfasts are to-die-for (Kurfürstenanlage 1, 69115 Heidelberg, tel. 011-49-6221-917651, www.crowneplaza-heidelberg.de ). Chapter II of A Tramp Abroad opens with a witty account of the Grand Duke (Friedrich I Wilhelm Ludwig (1826-1907) and Duchess of Baden's (Luise Marie Elisabeth (1838-1923) of Prussia) state visit to Heidelberg with the Empress of Germany (Marie Luise Augusta (1811-91)). Twain watched the meticulous preparations and train arrival from his hotel window on his first morning here.

He then goes on to marvel at the romantic ruins of the huge 800-year-old Gothic and Baroque Castle and a magnificent fireworks display — now put on three times a summer — which, like me, he watched in a downpour. Like Goethe who in 1816 wrote " West-oestliche Divan " in its magnificent gardens, Twain enjoyed his visits to the Castle. He was especially impressed with "the great Heidelberg Tun...a wine-cask as big as a cottage" which, although empty, "holds eighteen hundred thousand bottles" or 221,726 liters. He wonders tongue-in-cheek "what this cask could have been built for?" As a dance-floor or to produce German cream?

Although Twain doesn't mention him, behind the Tun on a plinth is a statue of the dwarf Perkeo who came from the South Tyrol and today is the symbol of Carnival in Heidelberg. He could reputedly hold a lot of drink, and served as court jester and Keeper of the Tun under Elector Carl Philipp (1716-42). According to legend, his name derives from his never-changing reply to the question of whether he would like one more glass of wine: " Perché no? " ("Why not?" in Italian). It is said that Perkeo died as a result of being talked into drinking a glass of water.

Today it's possible to book a Castle tour guided by English-speaking impersonators of Twain and Olivia at www.cvb-heidelberg.de, an invaluable multi-lingual site for all tourist information. However, they won't take you to the not-to-be-missed German Apothecary Museum because it wasn't at the Castle in their time. The most extensive exhibition of its kind in the world, it houses a unique collection of equipment, instruments, laboratory apparatus, vessels, medicines, documents and books relating to medicine and alchemy from the Middle Ages to the 19th century.

Founded in 1387, Heidelberg is Germany's oldest university. Twain attended lectures here and describes the freedom of student life, their informal, almost upper handed, relationship with professors, and the much-coveted stay in the Karzer or "Student Prison" for Town vs. Gown offenses, such as disturbing the peace, womanizing, unruly drunkenness, and setting the townspeople's ubiquitous pigs free. In use from 1712 to 1914 for sentences up to four weeks, its graffitied "cells" are now a crowded tourist venue ( Augustinergasse 2 ). Twain was particularly fascinated with the students' obsession for dueling and their inevitable scars. Although no longer practiced by today's c. 32,000 students (one-fifth of Heidelberg's population), it's possible to visit the dueling grounds at the Gasthaus zur Hirschgasse , today a bijou hotel with an excellent restaurant, "Le Gourmet". ( Hirschgasse 3, 69120 Heidelberg, tel. 011-49-6221-4540, www.hirschgasse.de ).

Although not mentioned in A Tramp Abroad , another splendid hotel with excellent food is the Ritter on Heidelberg's Hauptstrasse or Main Street, the longest pedestrian street in Germany, in the Altstadt or picturesque Old City opposite the impressive Gothic Heilig Geist Kirche or Church of the Holy Spirit on the Marktplatz or Market Square. Here Twain noted the wall between the nave and the choir built to separate Catholic worshippers from the Protestants. The Haus zum Ritter St. Georg (Knight's House) is the only private house to have survived the wars of the 17th century. A hotel since 1681, it was built in 1592 by the Huguenot cloth-dealer Carolus Belier and his wife Francesca who had come to Heidelberg to escape religious persecution. The vaulted rooms on the ground floor and in the cellar were originally storage rooms for Belier's wares, which could then be laid out for sale on the folded-down window shutters on the ground floor. (Hauptstrasse 178, 69117 Heidelberg, tel. 011-49-6221-1350), www.ritter-heidelberg.de ).

Besides dueling another student pastime has always been pub-crawling. The most famous student tavern is the Zum Roten Ochsen ("At the Red Oxen") ( Hauptstrasse 217, tel. 011-49-6221-20977 ), built in 1703 and owned by the Spengel family for the past 165 years. Others nearby include Schnookeloch on the Haspelgasse ( no.8, tel. 011-49-6221-138080 ) since 1735 and the Café Knösel (Haspelgasse 20, tel. 011-49-6221-22345 ) founded in 1863. A specialty on sale here are bitter-sweet chocolate cookies called " Heidelberger Studentenkusses " or "Student Kisses". Supposedly, in the past, when women were more tightly chaperoned, they accepted these chocolate confectioneries as a substitute for the real kisses they would rather have received.

Through its many scientific research centers, large student population, and Technology Park Heidelberg strives to be dynamic and keep up with the times. As an itinerant printer, publisher, and inventor of an avant-garde typesetting machine, Mark Twain would certainly have appreciated the ultra-modern Heidelberger Druckmaschinen's Print Media Academy. It aims to provide an ultra-modern international training forum for the latest printing technology ( For course listings in English and enrollment see www.print-media-academy.com ). In its forecourt is contemporary local artist Jürgen Goertz's "The S-Printing Horse", the world's largest sculpture of a horse. Its theme is rotation: of both the internal workings of printing presses and of the streams of movement in the cosmos.

On November 4, 2003 the world-famous chef Manfred Schwarz, considered one of the top ten best chefs in Germany opened his new, if a bit slick and pricey, restaurant, Schwarz Das Restaurant , on level 12, the Academy's top floor with magical panoramic views over the city. His legendary dish is " Schwarz'sche Saumagen , his personal interpretation of truffled innards; his concept of cuisine: Franco-Italian with a personal creative touch and regional ingredients. Formerly Schwarz was the personal chef of Helmut Kohl, the youngest sous-chef ever of the Republic of Germany, and chef at the Deidesheimer Hof . ( For reservations: tel. 011-49-6221-7570300 ).

After the Castle and "Student Prison", the Alte Brücke or Old Bridge and the Philosophenweg or Philosopher's Walk are Heidelberg's most popular sights. Twain only just refers to Heidelberg's bridges, but he had to have crossed the Alte Brücke , completed in 1788, to get to the dueling grounds on the Hirschgasse on the opposite bank of the River Neckar from the Old Town. Goethe had said that crossing the Neckar over the Old Bridge was the most beautiful view he'd ever encountered.

Goethe was not the only poet to find inspiration in Heidelberg. On the Philosophenweg or Philosopher's Walk above the Hirschgasse , with its woods, well-kept gardens, and famous view of old Heidelberg, the Muse visited Brentano, Eichendorff, von Scheffel, Hölderin, and Alan Ginsburg. Instead, Twain preferred walking from this beloved Schloss Hotel, no longer in business, to the summit of the Königstuhl mountain ("the King's Chair") where he rented a studio in a pretty little inn. On a typical day he tried to write there in seclusion from 10 to 3, but, when his close friend Joseph Twichell came in to visit in August, they began boating down the River Neckar to some of several medieval castles along its twisting banks: Hirschorn, Dilsberg, Hornberg, and Bad Wimpfen.

These boat trips (still popular today with Heidelberg's newest attraction being a solar ship) triggered Twain's fantasy. He imagined them as a mythical raft voyage like that of Huck and Jim on the Mississippi. Back in Heidelberg, his inspiration became Chapter 16 of stymied Huckleberry Finn , ending Twain's three-year writer's block. Thank you, Heidelberg, for one of the greatest novels in American literature, published in 1885 after a 10-year struggle!

EPILOGUE: Sadly, even after the success of Huckleberry Finn , Twain's writer's block and financial woes returned. During his residence in Hartford, he had been a partner in the publishing firm of Charles L. Webster and Co, which reaped a fortune through the sale of Grant's Memoirs (1885) and Twain's own writings, but bad publishing ventures and the investment of $200,000 in a unperfected typesetting machine drove him into bankruptcy (1894). To discharge his debts he made a lecturing tour of the world. The record of this trip Following the Equator (1897) to South Africa, India, and Australia has an undercurrent of bitterness not found in his earlier travel books.